13.2. Setting up LVM on three SCSI disks with striping
For this recipe, the setup has three SCSI disks that will be put
into a logical volume using LVM. The disks are at /dev/sda,
/dev/sdb, and /dev/sdc.
 | Note |
|---|
| |
It is not currently possible to add a disk to a
striped logical volume in LVM 1. Use LVM 2 with the
lvm 2 format metadata if you wish to be able to do
so able to do so.
|
13.2.1. Preparing the disk partitions
Before you can use a disk in a volume group you will have to
prepare it:
 | Warning! |
|---|
| |
The following will destroy any data on /dev/sda, /dev/sdb,
and /dev/sdc
|
Run pvcreate on the disks:
# pvcreate /dev/sda
# pvcreate /dev/sdb
# pvcreate /dev/sdc
|
This creates a volume group descriptor area (VGDA) at the start
of the disks.
13.2.2. Setup a Volume Group
Create a volume group
# vgcreate my_volume_group /dev/sda /dev/sdb /dev/sdc
|
Run vgdisplay to verify volume group
# vgdisplay
--- Volume Group ---
VG Name my_volume_group
VG Access read/write
VG Status available/resizable
VG # 1
MAX LV 256
Cur LV 0
Open LV 0
MAX LV Size 255.99 GB
Max PV 256
Cur PV 3
Act PV 3
VG Size 1.45 GB
PE Size 4 MB
Total PE 372
Alloc PE / Size 0 / 0
Free PE / Size 372/ 1.45 GB
VG UUID nP2PY5-5TOS-hLx0-FDu0-2a6N-f37x-0BME0Y
|
The most important things to verify are that the first
three items are correct and that the VG Size item is the
proper size for the amount of space in all four of your
disks.
13.2.3. Creating the Logical Volume
If the volume group looks correct, it is time to create a
logical volume on top of the volume group.
You can make the logical volume any size you like (up to the
size of the VG you are creating it on; it is similar to a
partition on a non LVM setup). For this example we will create
just a single logical volume of size 1GB on the volume group.
The logical volume will be a striped set using for the 4k stripe
size. This should increase the performance of the logical
volume.
# lvcreate -i3 -I4 -L1G -nmy_logical_volume my_volume_group
lvcreate -- rounding 1048576 KB to stripe boundary size 1056768 KB / 258 PE
lvcreate -- doing automatic backup of "my_volume_group"
lvcreate -- logical volume "/dev/my_volume_group/my_logical_volume" successfully created
|
| Note |
|---|
| |
If you create the logical volume with a '-i2' you will only
use two of the disks in your volume group. This is useful if
you want to create two logical volumes out of the same
physical volume, but we will not touch that in this recipe.
|
13.2.4. Create the File System
Create an ext2 file system on the logical volume
# mke2fs /dev/my_volume_group/my_logical_volume
mke2fs 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
132192 inodes, 264192 blocks
13209 blocks (5.00%) reserved for the super user
First data block=0
9 block groups
32768 blocks per group, 32768 fragments per group
14688 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
|
13.2.5. Test the File System
Mount the file system on the logical volume
# mount /dev/my_volume_group/my_logical_volume /mnt
|
and check to make sure everything looks correct
# df
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/hda1 1311552 628824 616104 51% /
/dev/my_volume_group/my_logical_volume
1040132 20 987276 0% /mnt
|
If everything worked properly, you should now have a logical
volume mounted at
/mnt.
