13.2. Setting up LVM on three SCSI disks with striping

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

1. Create a volume group

   # vgcreate my_volume_group /dev/sda /dev/sdb /dev/sdc

2. 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.