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Wednesday, April 20, 2011

OMG LVM

The system has six SCSI hard disks, /dev/sda - /dev/sdf. /dev/sda is used for the Debian Etch system itself, while we will use /dev/sdb - /dev/sdf for LVM and RAID. /dev/sdb - /dev/sdf each have 80GB of disk space. In the beginning we will act as if each has only 25GB of disk space (thus using only 25GB on each of them), and in the course of the tutorial we will "replace" our 25GB hard disks with 80GB hard disks, thus demonstrating how you can replace small hard disks with bigger ones in LVM.

2 LVM Layout

Basically LVM looks like this:

Scenario with details :

 

You have one or more physical volumes (/dev/sdb1 - /dev/sde1 in our example), and on these physical volumes you create one or more volume groups (e.g. fileserver), and in each volume group you can create one or more logical volumes. If you use multiple physical volumes, each logical volume can be bigger than one of the underlying physical volumes (but of course the sum of the logical volumes cannot exceed the total space offered by the physical volumes).
It is a good practice to not allocate the full space to logical volumes, but leave some space unused. That way you can enlarge one or more logical volumes later on if you feel the need for it.
In this example we will create a volume group called fileserver, and we will also create the logical volumes /dev/fileserver/share, /dev/fileserver/backup, and /dev/fileserver/media (which will use only half of the space offered by our physical volumes for now - that way we can switch to RAID1 later on (also described in this tutorial)).

3 Our First LVM Setup

Let's find out about our hard disks:
fdisk -l
The output looks like this:
server1:~# fdisk -l

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          18      144553+  83  Linux
/dev/sda2              19        2450    19535040   83  Linux
/dev/sda4            2451        2610     1285200   82  Linux swap / Solaris

Disk /dev/sdb: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn't contain a valid partition table

Disk /dev/sdc: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdc doesn't contain a valid partition table

Disk /dev/sdd: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdd doesn't contain a valid partition table

Disk /dev/sde: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sde doesn't contain a valid partition table

Disk /dev/sdf: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdf doesn't contain a valid partition table
There are no partitions yet on /dev/sdb - /dev/sdf.
 We will create the partitions /dev/sdb1, /dev/sdc1, /dev/sdd1, and /dev/sde1 and leave /dev/sdf untouched for now. We act as if our hard disks had only 25GB of space instead of 80GB for now, therefore we assign 25GB to /dev/sdb1, /dev/sdc1, /dev/sdd1, and /dev/sde1:
fdisk /dev/sdb
server1:~# fdisk /dev/sdb

The number of cylinders for this disk is set to 10443.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): <-- n
Command action
   e   extended
   p   primary partition (1-4)
<-- p
Partition number (1-4): <-- 1
First cylinder (1-10443, default 1): <--
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-10443, default 10443): <-- +25000M

Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes): <-- L

 0  Empty           1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot
 1  FAT12           24  NEC DOS         81  Minix / old Lin bf  Solaris
 2  XENIX root      39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 5  Extended        41  PPC PReP Boot   85  Linux extended  c7  Syrinx
 6  FAT16           42  SFS             86  NTFS volume set da  Non-FS data
 7  HPFS/NTFS       4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
 8  AIX             4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility
 9  AIX bootable    4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt
 a  OS/2 Boot Manag 50  OnTrack DM      93  Amoeba          e1  DOS access
 b  W95 FAT32       51  OnTrack DM6 Aux 94  Amoeba 
BBT      e3  DOS R/O
 c  W95 FAT32 (LBA) 52  CP/M            9f  BSD/OS          e4  SpeedStor
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a0  
IBM Thinkpad hi eb  BeOS fs
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  EFI 
GPT
10  OPUS            55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor
14  Hidden FAT16 <3 61  SpeedStor       a9  NetBSD          f4  SpeedStor
16  Hidden FAT16    63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fd  Linux raid auto
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fe  LANstep
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid ff  
BBT
1c  Hidden W95 FAT3 75  PC/IX
Hex code (type L to list codes): <-- 8e
Changed system type of partition 1 to 8e (Linux LVM)

Command (m for help): <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
Now we do the same for the hard disks /dev/sdc - /dev/sde:
fdisk /dev/sdc
fdisk /dev/sdd
fdisk /dev/sde
Then run
fdisk -l
again. The output should look like this:
server1:~# fdisk -l

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          18      144553+  83  Linux
/dev/sda2              19        2450    19535040   83  Linux
/dev/sda4            2451        2610     1285200   82  Linux swap / Solaris

Disk /dev/sdb: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        3040    24418768+  8e  Linux LVM

Disk /dev/sdc: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1        3040    24418768+  8e  Linux LVM

Disk /dev/sdd: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1        3040    24418768+  8e  Linux LVM

Disk /dev/sde: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sde1               1        3040    24418768+  8e  Linux LVM

Disk /dev/sdf: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdf doesn't contain a valid partition table
Now we prepare our new partitions for LVM:
pvcreate /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
server1:~# pvcreate /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdc1" successfully created
  Physical volume "/dev/sdd1" successfully created
  Physical volume "/dev/sde1" successfully created
Let's revert this last action for training purposes:
pvremove /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
server1:~# pvremove /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
  Labels on physical volume "/dev/sdb1" successfully wiped
  Labels on physical volume "/dev/sdc1" successfully wiped
  Labels on physical volume "/dev/sdd1" successfully wiped
  Labels on physical volume "/dev/sde1" successfully wiped
Then run
pvcreate /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
again:
server1:~# pvcreate /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdc1" successfully created
  Physical volume "/dev/sdd1" successfully created
  Physical volume "/dev/sde1" successfully created
Now run
pvdisplay
to learn about the current state of your physical volumes:
server1:~# pvdisplay
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name
  PV Size               23.29 GB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               G8lu2L-Hij1-NVde-sOKc-OoVI-fadg-Jd1vyU

  --- NEW Physical volume ---
  PV Name               /dev/sdc1
  VG Name
  PV Size               23.29 GB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               40GJyh-IbsI-pzhn-TDRq-PQ3l-3ut0-AVSE4B

  --- NEW Physical volume ---
  PV Name               /dev/sdd1
  VG Name
  PV Size               23.29 GB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               4mU63D-4s26-uL00-r0pO-Q0hP-mvQR-2YJN5B

  --- NEW Physical volume ---
  PV Name               /dev/sde1
  VG Name
  PV Size               23.29 GB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               3upcZc-4eS2-h4r4-iBKK-gZJv-AYt3-EKdRK6

Now let's create our volume group fileserver and add /dev/sdb1 - /dev/sde1 to it:

vgcreate fileserver /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
server1:~# vgcreate fileserver /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
  Volume group "fileserver" successfully created
Let's learn about our volume groups:
vgdisplay
server1:~# vgdisplay
  --- Volume group ---
  VG Name               fileserver
  System ID
  Format                lvm2
  Metadata Areas        4
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  
MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                4
  Act PV                4
  VG Size               93.14 GB
  PE Size               4.00 MB
  Total PE              23844
  Alloc PE / Size       0 / 0
  Free  PE / Size       23844 / 93.14 GB
  VG UUID               3Y1WVF-BLET-QkKs-Qnrs-SZxI-wrNO-dTqhFP
Another command to learn about our volume groups:
vgscan
server1:~# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "fileserver" using metadata type lvm2
For training purposes let's rename our volumegroup fileserver into data:
vgrename fileserver data
server1:~# vgrename fileserver data
  Volume group "fileserver" successfully renamed to "data"
Let's run vgdisplay and vgscan again to see if the volume group has been renamed:
vgdisplay
server1:~# vgdisplay
  --- Volume group ---
  VG Name               data
  System ID
  Format                lvm2
  Metadata Areas        4
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  
MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                4
  Act PV                4
  VG Size               93.14 GB
  PE Size               4.00 MB
  Total PE              23844
  Alloc PE / Size       0 / 0
  Free  PE / Size       23844 / 93.14 GB
  VG UUID               3Y1WVF-BLET-QkKs-Qnrs-SZxI-wrNO-dTqhFP
vgscan
server1:~# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "data" using metadata type lvm2
Now let's delete our volume group data:
vgremove data
server1:~# vgremove data
  Volume group "data" successfully removed
vgdisplay      
No output this time:
server1:~# vgdisplay
vgscan
server1:~# vgscan
  Reading all physical volumes.  This may take a while...
Let's create our volume group fileserver again:
vgcreate fileserver /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
server1:~# vgcreate fileserver /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
  Volume group "fileserver" successfully created
Next we create our logical volumes share (40GB), backup (5GB), and media (1GB) in the volume group fileserver. Together they use a little less than 50% of the available space (that way we can make use of RAID1 later on):
lvcreate --name share --size 40G fileserver
server1:~# lvcreate --name share  --size 40G fileserver
  Logical volume "share" created
lvcreate --name backup --size 5G fileserver
server1:~# lvcreate --name backup --size  5G fileserver
  Logical volume "backup" created
lvcreate --name media --size 1G fileserver
server1:~# lvcreate --name media  --size  1G fileserver
  Logical volume "media" created
Let's get an overview of our logical volumes:
lvdisplay
server1:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/fileserver/share
  VG Name                fileserver
  LV UUID                280Mup-H9aa-sn0S-AXH3-04cP-V6p9-lfoGgJ
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                40.00 GB
  Current LE             10240
  Segments               2
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:0

  --- Logical volume ---
  LV Name                /dev/fileserver/backup
  VG Name                fileserver
  LV UUID                zZeuKg-Dazh-aZMC-Aa99-KUSt-J6ET-KRe0cD
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                5.00 GB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1

  --- Logical volume ---
  LV Name                /dev/fileserver/media
  VG Name                fileserver
  LV UUID                usfvrv-BC92-3pFH-2NW0-2N3e-6ERQ-4Sj7YS
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                1.00 GB
  Current LE             256
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2
lvscan
server1:~# lvscan
  ACTIVE            '/dev/fileserver/share' [40.00 GB] inherit
  ACTIVE            '/dev/fileserver/backup' [5.00 GB] inherit
  ACTIVE            '/dev/fileserver/media' [1.00 GB] inherit
For training purposes we rename our logical volume media into films:
lvrename fileserver media films
server1:~# lvrename fileserver media films
  Renamed "media" to "films" in volume group "fileserver"
lvdisplay
server1:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/fileserver/share
  VG Name                fileserver
  LV UUID                280Mup-H9aa-sn0S-AXH3-04cP-V6p9-lfoGgJ
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                40.00 GB
  Current LE             10240
  Segments               2
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:0

  --- Logical volume ---
  LV Name                /dev/fileserver/backup
  VG Name                fileserver
  LV UUID                zZeuKg-Dazh-aZMC-Aa99-KUSt-J6ET-KRe0cD
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                5.00 GB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1

  --- Logical volume ---
  LV Name                /dev/fileserver/films
  VG Name                fileserver
  LV UUID                usfvrv-BC92-3pFH-2NW0-2N3e-6ERQ-4Sj7YS
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                1.00 GB
  Current LE             256
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2
lvscan
server1:~# lvscan
  ACTIVE            '/dev/fileserver/share' [40.00 GB] inherit
  ACTIVE            '/dev/fileserver/backup' [5.00 GB] inherit
  ACTIVE            '/dev/fileserver/films' [1.00 GB] inherit
Next let's delete the logical volume films:
lvremove /dev/fileserver/films
server1:~# lvremove /dev/fileserver/films
Do you really want to remove active logical volume "films"? [y/n]: <-- y
  Logical volume "films" successfully removed
We create the logical volume media again:
lvcreate --name media --size 1G fileserver
server1:~# lvcreate --name media  --size  1G fileserver
  Logical volume "media" created
Now let's enlarge media from 1GB to 1.5GB:
lvextend -L1.5G /dev/fileserver/media
server1:~# lvextend -L1.5G /dev/fileserver/media
  Extending logical volume media to 1.50 GB
  Logical volume media successfully resized
Let's shrink it to 1GB again:
lvreduce -L1G /dev/fileserver/media
server1:~# lvreduce -L1G /dev/fileserver/media
  WARNING: Reducing active logical volume to 1.00 GB
  THIS 
MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce media? [y/n]: <-- y
  Reducing logical volume media to 1.00 GB
  Logical volume media successfully resized


Until now we have three logical volumes, but we don't have any filesystems in them, and without a filesystem we can't save anything in them. Therefore we create an ext3 filesystem in share, an xfs filesystem in backup, and a reiserfs filesystem in media:

mkfs.ext3 /dev/fileserver/share

server1:~# mkfs.ext3 /dev/fileserver/share
mke2fs 1.40-WIP (14-Nov-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
5242880 inodes, 10485760 blocks
524288 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
320 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done


This filesystem will be automatically checked every 23 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
mkfs.xfs /dev/fileserver/backup
server1:~# mkfs.xfs /dev/fileserver/backup
meta-data=/dev/fileserver/backup isize=256    agcount=8, agsize=163840 blks
         =                       sectsz=512   attr=0
data     =                       bsize=4096   blocks=1310720, imaxpct=25
         =                       sunit=0      swidth=0 blks, unwritten=1
naming   =version 2              bsize=4096
log      =internal log           bsize=4096   blocks=2560, version=1
         =                       sectsz=512   sunit=0 blks
realtime =none                   extsz=65536  blocks=0, rtextents=0
mkfs.reiserfs /dev/fileserver/media
server1:~# mkfs.reiserfs /dev/fileserver/media
mkfs.reiserfs 3.6.19 (2003 www.namesys.com)

A pair of credits:
Alexander  Lyamin  keeps our hardware  running,  and was very  generous  to our
project in many little ways.

Chris Mason wrote the journaling code for V3,  which was enormously more useful
to users than just waiting until  we could create a wandering log filesystem as
Hans would have unwisely done without him.
Jeff Mahoney optimized the bitmap  scanning code for V3,  and performed the big
endian cleanups.


Guessing about desired format.. Kernel 2.6.17-2-486 is running.
Format 3.6 with standard journal
Count of blocks on the device: 262144
Number of blocks consumed by mkreiserfs formatting process: 8219
Blocksize: 4096
Hash function used to sort names: "r5"
Journal Size 8193 blocks (first block 18)
Journal Max transaction length 1024
inode generation number: 0
UUID: 2bebf750-6e05-47b2-99b6-916fa7ea5398
ATTENTION: YOU SHOULD REBOOT AFTER FDISK!
        
ALL DATA WILL BE LOST ON '/dev/fileserver/media'!
Continue (y/n):y
Initializing journal - 0%....20%....40%....60%....80%....100%
Syncing..ok

Tell your friends to use a kernel based on 2.4.18 or later, and especially not a
kernel based on 2.4.9, when you use reiserFS. Have fun.

ReiserFS is successfully created on /dev/fileserver/media.
Now we are ready to mount our logical volumes. I want to mount share in /var/share, backup in /var/backup, and media in /var/media, therefore we must create these directories first:
mkdir /var/media /var/backup /var/share
Now we can mount our logical volumes:
mount /dev/fileserver/share /var/share
mount /dev/fileserver/backup /var/backup
mount /dev/fileserver/media /var/media
Now run
df -h
You should see your logical volumes in the output:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-share
                       40G  177M   38G   1% /var/share
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
Congratulations, you've just set up your first LVM system! You can now write to and read from /var/share, /var/backup, and /var/media as usual.
We have mounted our logical volumes manually, but of course we'd like to have them mounted automatically when the system boots. Therefore we modify /etc/fstab:
mv /etc/fstab /etc/fstab_orig
cat /dev/null > /etc/fstab
vi /etc/fstab
Put the following into it:
# /etc/fstab: static file system information.
#
#              
proc            /proc           proc    defaults        0       0
/dev/sda2       /               ext3    defaults,errors=remount-ro 0       1
/dev/sda1       /boot           ext3    defaults        0       2
/dev/hdc        /media/cdrom0   udf,iso9660 user,noauto     0       0
/dev/fd0        /media/floppy0  auto    rw,user,noauto  0       0
/dev/fileserver/share   /var/share     ext3       rw,noatime    0 0
/dev/fileserver/backup    /var/backup      xfs        rw,noatime    0 0
/dev/fileserver/media    /var/media      reiserfs   rw,noatime    0 0
If you compare it to our backup of the original file, /etc/fstab_orig, you will notice that we added the lines:
/dev/fileserver/share   /var/share     ext3       rw,noatime    0 0
/dev/fileserver/backup    /var/backup      xfs        rw,noatime    0 0
/dev/fileserver/media    /var/media      reiserfs   rw,noatime    0 0
Now we reboot the system:
shutdown -r now
After the system has come up again, run
df -h
again. It should still show our logical volumes in the output:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-share
                       40G  177M   38G   1% /var/share
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
In this chapter we will learn how to resize our logical volume share which has an ext3 filesystem. (I will show how to resize logical volumes with xfs and reiserfs filesystems further down this tutorial.)

First we must unmount it:
umount /var/share
share should not be listed anymore in the
df -h
output:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
Now let's enlarge share from 40GB to 50GB:
lvextend -L50G /dev/fileserver/share
server1:~# lvextend -L50G /dev/fileserver/share
  Extending logical volume share to 50.00 GB
  Logical volume share successfully resized
Until now we have enlarged only share, but not the ext3 filesystem on share. This is what we do now:
e2fsck -f /dev/fileserver/share
server1:~# e2fsck -f /dev/fileserver/share
e2fsck 1.40-WIP (14-Nov-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/fileserver/share: 11/5242880 files (9.1% non-contiguous), 209588/10485760 blocks
Make a note of the total amount of blocks (10485760) because we need it when we shrink share later on.
resize2fs /dev/fileserver/share
server1:~# resize2fs /dev/fileserver/share
resize2fs 1.40-WIP (14-Nov-2006)
Resizing the filesystem on /dev/fileserver/share to 13107200 (4k) blocks.
The filesystem on /dev/fileserver/share is now 13107200 blocks long.
Let's mount share:
mount /dev/fileserver/share /var/share
and in the
df -h
output share should now have 50GB instead of 40:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
/dev/mapper/fileserver-share
                       50G  180M   47G   1% /var/share
Shrinking a logical volume is the other way round: first we must shrink the filesystem before we reduce the logical volume's size. Let's shrink share to 40GB again:
umount /var/share
df -h
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
e2fsck -f /dev/fileserver/share
server1:~# e2fsck -f /dev/fileserver/share
e2fsck 1.40-WIP (14-Nov-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/fileserver/share: 11/6553600 files (9.1% non-contiguous), 251733/13107200 blocks
When resizing an ext3 filesystem to a certain size (instead of all available space), resize2fs takes the number of blocks as argument (you can as well specify the new size in MB, etc. See
man resize2fs
for more details). From our previous operation we know the 40GB equals 10485760 blocks so we run
resize2fs /dev/fileserver/share 10485760
server1:~# resize2fs /dev/fileserver/share 10485760
resize2fs 1.40-WIP (14-Nov-2006)
Resizing the filesystem on /dev/fileserver/share to 10485760 (4k) blocks.
The filesystem on /dev/fileserver/share is now 10485760 blocks long
.
We've shrinked the filesystem, now we must shrink the logical volume, too:
lvreduce -L40G /dev/fileserver/share
server1:~# lvreduce -L40G /dev/fileserver/share
  WARNING: Reducing active logical volume to 40.00 GB
  THIS 
MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce share? [y/n]: <-- y
  Reducing logical volume share to 40.00 GB
  Logical volume share successfully resized
We can ignore the warning that data might be destroyed because we have shrinked the filesystem before.
Let's mount share again:
mount /dev/fileserver/share /var/share
The output of
df -h
should now look like this:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
/dev/mapper/fileserver-share
                       40G  177M   38G   1% /var/share

We haven't used /dev/sdf until now. We will now create the partition /dev/sdf1 (25GB) and add that to our fileserver volume group.

fdisk /dev/sdf
server1:~# fdisk /dev/sdf
Device contains neither a valid DOS partition table, nor Sun, 
SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.


The number of cylinders for this disk is set to 10443.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): <-- n
Command action
   e   extended
   p   primary partition (1-4)
<-- p
Partition number (1-4): <-- 1
First cylinder (1-10443, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-10443, default 10443): <-- +25000M

Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes): <-- 8e
Changed system type of partition 1 to 8e (Linux LVM)

Command (m for help): <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
Let's prepare /dev/sdf1 for LVM:
pvcreate /dev/sdf1
server1:~# pvcreate /dev/sdf1
  Physical volume "/dev/sdf1" successfully created
Add /dev/sdf1 to our fileserver volume group:
vgextend fileserver /dev/sdf1
Run
vgdisplay
VG Size should now be bigger than before:
server1:~# vgdisplay
  --- Volume group ---
  VG Name               fileserver
  System ID
  Format                lvm2
  Metadata Areas        5
  Metadata Sequence No  12
  VG Access             read/write
  VG Status             resizable
  
MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                5
  Act PV                5
  VG Size               116.43 GB
  PE Size               4.00 MB
  Total PE              29805
  Alloc PE / Size       11776 / 46.00 GB
  Free  PE / Size       18029 / 70.43 GB
  VG UUID               iWr1Vk-7h7J-hLRL-SHbx-3p87-Rq47-L1GyEO
That's it. /dev/sdf1 has been added to the fileserver volume group.
Now let's remove /dev/sdb1. Before we do this, we must copy all data on it to /dev/sdf1:
pvmove /dev/sdb1 /dev/sdf1
This can take some minutes:
server1:~# pvmove /dev/sdb1 /dev/sdf1
  /dev/sdb1: Moved: 1.9%
  /dev/sdb1: Moved: 3.8%
  /dev/sdb1: Moved: 5.8%
  /dev/sdb1: Moved: 7.8%
  /dev/sdb1: Moved: 9.7%
  /dev/sdb1: Moved: 11.6%
  /dev/sdb1: Moved: 13.6%
  /dev/sdb1: Moved: 15.6%
  /dev/sdb1: Moved: 17.5%
  /dev/sdb1: Moved: 19.4%
  /dev/sdb1: Moved: 21.4%
  [...]
  /dev/sdb1: Moved: 85.7%
  /dev/sdb1: Moved: 87.7%
  /dev/sdb1: Moved: 89.7%
  /dev/sdb1: Moved: 91.7%
  /dev/sdb1: Moved: 93.6%
  /dev/sdb1: Moved: 95.5%
  /dev/sdb1: Moved: 97.5%
  /dev/sdb1: Moved: 99.4%
  /dev/sdb1: Moved: 100.0%
Next we remove /dev/sdb1 from the fileserver volume group:
vgreduce fileserver /dev/sdb1
server1:~# vgreduce fileserver /dev/sdb1
  Removed "/dev/sdb1" from volume group "fileserver"
vgdisplay
server1:~# vgdisplay
  --- Volume group ---
  VG Name               fileserver
  System ID
  Format                lvm2
  Metadata Areas        4
  Metadata Sequence No  16
  VG Access             read/write
  VG Status             resizable
  
MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                4
  Act PV                4
  VG Size               93.14 GB
  PE Size               4.00 MB
  Total PE              23844
  Alloc PE / Size       11776 / 46.00 GB
  Free  PE / Size       12068 / 47.14 GB
  VG UUID               iWr1Vk-7h7J-hLRL-SHbx-3p87-Rq47-L1GyEO
Then we run
pvremove /dev/sdb1
/dev/sdb1 shouldn't be listed as a physical volume anymore:
pvdisplay
server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               1682
  Allocated PE          4279
  PV UUID               40GJyh-IbsI-pzhn-TDRq-PQ3l-3ut0-AVSE4B

  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               4681
  Allocated PE          1280
  PV UUID               4mU63D-4s26-uL00-r0pO-Q0hP-mvQR-2YJN5B

  --- Physical volume ---
  PV Name               /dev/sde1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               5705
  Allocated PE          256
  PV UUID               3upcZc-4eS2-h4r4-iBKK-gZJv-AYt3-EKdRK6

  --- Physical volume ---
  PV Name               /dev/sdf1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               0
  Allocated PE          5961
  PV UUID               1xgo2I-SBjj-0MAz-lmDu-OLZ1-3NdO-mLkS20
You could now remove /dev/sdb from the system (if this was a real system and not a virtual machine).

In this chapter we will undo all changes from the previous chapters to return to the system's original state. This is just for training purposes so that you learn how to undo an LVM setup.
First we must unmount our logical volumes:
umount /var/share
umount /var/backup
umount /var/media
df -h
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  665M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   92K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
Then we delete each of them:
lvremove /dev/fileserver/share
server1:~# lvremove /dev/fileserver/share
Do you really want to remove active logical volume "share"? [y/n]: <-- y
  Logical volume "share" successfully removed
lvremove /dev/fileserver/backup
server1:~# lvremove /dev/fileserver/backup
Do you really want to remove active logical volume "backup"? [y/n]: <-- y
  Logical volume "backup" successfully removed
lvremove /dev/fileserver/media
server1:~# lvremove /dev/fileserver/media
Do you really want to remove active logical volume "media"? [y/n]: <-- y
  Logical volume "media" successfully removed
Next we remove the volume group fileserver:
vgremove fileserver
server1:~# vgremove fileserver
  Volume group "fileserver" successfully removed
Finally we do this:
pvremove /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1
server1:~# pvremove  /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1
  Labels on physical volume "/dev/sdc1" successfully wiped
  Labels on physical volume "/dev/sdd1" successfully wiped
  Labels on physical volume "/dev/sde1" successfully wiped
  Labels on physical volume "/dev/sdf1" successfully wiped
vgdisplay
server1:~# vgdisplay
  No volume groups found
pvdisplay
should display nothing at all:
server1:~# pvdisplay
Now we must undo our changes in /etc/fstab to avoid that the system tries to mount non-existing devices. Fortunately we have made a backup of the original file that we can copy back now:
mv /etc/fstab_orig /etc/fstab
Reboot the system:
shutdown -r now
Afterwards the output of
df -h
should look like this:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  666M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   92K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
Now the system is like it was in the beginning (except that the partitions /dev/sdb1 - /dev/sdf1 still exist - you could delete them with fdisk but we don't do this now - as well as the directories /var/share, /var/backup, and /var/media which we also don't delete).

7 LVM On RAID1
In this chapter we will set up LVM again and move it to a RAID1 array to guarantee for high-availability. In the end this should look like this:



This means we will make the RAID array /dev/md0 from the partitions /dev/sdb1 + /dev/sdc1, and the RAID array /dev/md1 from the partitions /dev/sdd1 + /dev/sde1. /dev/md0 and /dev/md1 will then be the physical volumes for LVM.
Before we come to that, we set up LVM as before:
pvcreate /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
vgcreate fileserver /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
lvcreate --name share --size 40G fileserver
lvcreate --name backup --size 5G fileserver
lvcreate --name media --size 1G fileserver
mkfs.ext3 /dev/fileserver/share
mkfs.xfs /dev/fileserver/backup
mkfs.reiserfs /dev/fileserver/media
Then we mount our logical volumes:
mount /dev/fileserver/share /var/share
mount /dev/fileserver/backup /var/backup
mount /dev/fileserver/media /var/media
The output of
df -h
should now look like this:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  666M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   92K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-share
                       40G  177M   38G   1% /var/share
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.0G   33M  992M   4% /var/media
Now we must move the contents of /dev/sdc1 and /dev/sde1 (/dev/sdc1 is the second partition of our future /dev/md0, /dev/sde1 the second partition of our future /dev/md1) to the remaining partitions, because we will afterwards remove them from LVM and format them with the type fd (Linux RAID autodetect) and move them to /dev/md0 resp. /dev/md1.
modprobe dm-mirror
pvmove /dev/sdc1
vgreduce fileserver /dev/sdc1
pvremove /dev/sdc1
pvdisplay
server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               0
  Allocated PE          5961
  PV UUID               USDJyG-
VDM2-r406-OjQo-h3eb-c9Mp-4nvnvu

  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               4681
  Allocated PE          1280
  PV UUID               qdEB5d-389d-O5UA-Kbwv-mn1y-74FY-4zublN

  --- Physical volume ---
  PV Name               /dev/sde1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               1426
  Allocated PE          4535
  PV UUID               4vL1e0-sr2M-awGd-qDJm-ZrC9-wuxW-2lEqp2
pvmove /dev/sde1
vgreduce fileserver /dev/sde1
pvremove /dev/sde1
pvdisplay
server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               0
  Allocated PE          5961
  PV UUID               USDJyG-
VDM2-r406-OjQo-h3eb-c9Mp-4nvnvu

  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               146
  Allocated PE          5815
  PV UUID               qdEB5d-389d-O5UA-Kbwv-mn1y-74FY-4zublN
Now we format /dev/sdc1 with the type fd (Linux RAID autodetect):
fdisk /dev/sdc
server1:~# fdisk /dev/sdc

The number of cylinders for this disk is set to 10443.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes): <-- L

 0  Empty           1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot
 1  FAT12           24  NEC DOS         81  Minix / old Lin bf  Solaris
 2  XENIX root      39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 5  Extended        41  PPC PReP Boot   85  Linux extended  c7  Syrinx
 6  FAT16           42  SFS             86  NTFS volume set da  Non-FS data
 7  HPFS/NTFS       4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
 8  AIX             4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility
 9  AIX bootable    4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt
 a  OS/2 Boot Manag 50  OnTrack DM      93  Amoeba          e1  DOS access
 b  W95 FAT32       51  OnTrack DM6 Aux 94  Amoeba 
BBT      e3  DOS R/O
 c  W95 FAT32 (LBA) 52  CP/M            9f  BSD/OS          e4  SpeedStor
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a0  
IBM Thinkpad hi eb  BeOS fs
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  EFI 
GPT
10  OPUS            55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor
14  Hidden FAT16 <3 61  SpeedStor       a9  NetBSD          f4  SpeedStor
16  Hidden FAT16    63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fd  Linux raid auto
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fe  LANstep
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid ff  
BBT
1c  Hidden W95 FAT3 75  PC/IX
Hex code (type L to list codes): <-- fd
Changed system type of partition 1 to fd (Linux raid autodetect)

Command (m for help): <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
Now do the same with /dev/sde1:
fdisk /dev/sde
The output of
fdisk -l
should now look like this:
server1:~# fdisk -l

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          18      144553+  83  Linux
/dev/sda2              19        2450    19535040   83  Linux
/dev/sda4            2451        2610     1285200   82  Linux swap / Solaris

Disk /dev/sdb: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        3040    24418768+  8e  Linux LVM

Disk /dev/sdc: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1        3040    24418768+  fd  Linux raid autodetect

Disk /dev/sdd: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1        3040    24418768+  8e  Linux LVM

Disk /dev/sde: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sde1               1        3040    24418768+  fd  Linux raid autodetect

Disk /dev/sdf: 85.8 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdf1               1        3040    24418768+  8e  Linux LVM
Next we add /dev/sdc1 to /dev/md0 and /dev/sde1 to /dev/md1. Because the second nodes (/dev/sdb1 and /dev/sdd1) are not ready yet, we must specify missing in the following commands:
mdadm --create /dev/md0 --auto=yes -l 1 -n 2 /dev/sdc1 missing
server1:~# mdadm --create /dev/md0 --auto=yes -l 1 -n 2 /dev/sdc1 missing
mdadm: array /dev/md0 started.
mdadm --create /dev/md1 --auto=yes -l 1 -n 2 /dev/sde1 missing
server1:~# mdadm --create /dev/md1 --auto=yes -l 1 -n 2 /dev/sde1 missing
mdadm: array /dev/md1 started.
Afterwards we prepare /dev/md0 and /dev/md1 for LVM:
pvcreate /dev/md0 /dev/md1
server1:~# pvcreate /dev/md0 /dev/md1
  Physical volume "/dev/md0" successfully created
  Physical volume "/dev/md1" successfully created
and extend our fileserver volume group:
vgextend fileserver /dev/md0 /dev/md1
server1:~# vgextend fileserver /dev/md0 /dev/md1
  Volume group "fileserver" successfully extended
The outputs of
Pvdisplay  and vgdisplay should look like this:
server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               0
  Allocated PE          5961
  PV UUID               USDJyG-
VDM2-r406-OjQo-h3eb-c9Mp-4nvnvu

  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               146
  Allocated PE          5815
  PV UUID               qdEB5d-389d-O5UA-Kbwv-mn1y-74FY-4zublN

  --- Physical volume ---
  PV Name               /dev/md0
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               5961
  Allocated PE          0
  PV UUID               7JHUXF-1R2p-OjbJ-X1OT-uaeg-gWRx-H6zx3P

  --- Physical volume ---
  PV Name               /dev/md1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               5961
  Allocated PE          0
  PV UUID               pwQ5AJ-RwVK-EebA-0Z13-d27d-2IdP-HqT5RW
server1:~# vgdisplay
  --- Volume group ---
  VG Name               fileserver
  System ID
  Format                lvm2
  Metadata Areas        4
  Metadata Sequence No  14
  VG Access             read/write
  VG Status             resizable
  
MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                4
  Act PV                4
  VG Size               93.14 GB
  PE Size               4.00 MB
  Total PE              23844
  Alloc PE / Size       11776 / 46.00 GB
  Free  PE / Size       12068 / 47.14 GB
  VG UUID               dQDEHT-kNHf-UjRm-rmJ3-OUYx-9G1t-aVskI1
Now we move the contents of /dev/sdb1 to /dev/md0 and the contents of /dev/sdd1 to /dev/md1, then we remove /dev/sdb1 and /dev/sdd1 from LVM:


pvmove /dev/sdb1 /dev/md0
pvmove /dev/sdd1 /dev/md1
vgreduce fileserver /dev/sdb1 /dev/sdd1
pvremove /dev/sdb1 /dev/sdd1
Now only /dev/md0 and /dev/md1 should be left as physical volumes:
pvdisplay
server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/md0
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               0
  Allocated PE          5961
  PV UUID               7JHUXF-1R2p-OjbJ-X1OT-uaeg-gWRx-H6zx3P

  --- Physical volume ---
  PV Name               /dev/md1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               146
  Allocated PE          5815
  PV UUID               pwQ5AJ-RwVK-EebA-0Z13-d27d-2IdP-HqT5RW
Now we format /dev/sdb1 with fd (Linux RAID autodetect):
fdisk /dev/sdb
server1:~# fdisk /dev/sdb

The number of cylinders for this disk is set to 32635.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes): <-- fd
Changed system type of partition 1 to fd (Linux raid autodetect)

Command (m for help): <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
Do the same with /dev/sdd1:
fdisk /dev/sdd
Next add /dev/sdb1 to /dev/md0 and /dev/sdd1 to /dev/md1:
mdadm --manage /dev/md0 --add /dev/sdb1
server1:~# mdadm --manage /dev/md0 --add /dev/sdb1
mdadm: added /dev/sdb1
mdadm --manage /dev/md1 --add /dev/sdd1
server1:~# mdadm --manage /dev/md1 --add /dev/sdd1
mdadm: added /dev/sdd1
Now the two RAID arrays will be synchronized. This will take some time, you can check with
cat /proc/mdstat
when the process is finished. The output looks like this for an unfinished process:
server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md1 : active raid1 sdd1[2] sde1[0]
      24418688 blocks [2/1] [U_]
      [=>...................]  recovery =  6.4% (1586560/24418688) finish=1.9min speed=198320K/sec

md0 : active raid1 sdb1[2] sdc1[0]
      24418688 blocks [2/1] [U_]
      [==>..................]  recovery = 10.5% (2587264/24418688) finish=2.8min speed=129363K/sec

unused devices: 
and like this when the process is finished:
server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md1 : active raid1 sdd1[1] sde1[0]
      24418688 blocks [2/2] [UU]

md0 : active raid1 sdb1[1] sdc1[0]
      24418688 blocks [2/2] [UU]

unused devices: 
If you have a look at PV Size in the output of
pvdisplay
you will see that 2 * 23.29GB = 46.58GB are available, however only 40GB (share) + 5GB (backup) + 1GB (media) = 46GB are used which means we could extend one of our logical devices with about 0.5GB. I've already shown how to extend an ext3 logical volume (share), so we will resize media now which uses reiserfs. reiserfs filesystems can be resized without unmounting:
lvextend -L1.5G /dev/fileserver/media
server1:~# lvextend -L1.5G /dev/fileserver/media
  Extending logical volume media to 1.50 GB
  Logical volume media successfully resized
resize_reiserfs /dev/fileserver/media           
server1:~# resize_reiserfs /dev/fileserver/media
resize_reiserfs 3.6.19 (2003 www.namesys.com)

resize_reiserfs: On-line resizing finished successfully.
The output of
df -h
looks like this:
server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              19G  666M   17G   4% /
tmpfs                  78M     0   78M   0% /lib/init/rw
udev                   10M   92K   10M   1% /dev
tmpfs                  78M     0   78M   0% /dev/shm
/dev/sda1             137M   17M  114M  13% /boot
/dev/mapper/fileserver-share
                       40G  177M   38G   1% /var/share
/dev/mapper/fileserver-backup
                      5.0G  144K  5.0G   1% /var/backup
/dev/mapper/fileserver-media
                      1.5G   33M  1.5G   3% /var/media
If we want our logical volumes to be mounted automatically at boot time, we must modify /etc/fstab again (like in chapter 3):
mv /etc/fstab /etc/fstab_orig
cat /dev/null > /etc/fstab
vi /etc/fstab