Linux - How to add a new disk to a volume group
The disk to add to the VG can be a single disk or a hardware raid of disks that can be seen by the fdisk command
fdisk -l
The truncated output from this command is shown below
Disk /dev/sda: 146.6 GB, 146694733824 bytes 255 heads, 63 sectors/track, 17834 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 17 136521 83 Linux /dev/sda2 18 17834 143115052+ 8e Linux LVM Disk /dev/sdb: 293.3 GB, 293389467648 bytes 255 heads, 63 sectors/track, 35669 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk /dev/sdb doesn't contain a valid partition table
We can see that the disk /dev/sdb is not in use
We now need to create a partition on this disk using the fdisk command as follows
fdisk /dev/sdb
Command (m for help): p Disk /dev/sdb: 293.3 GB, 293389467648 bytes 255 heads, 63 sectors/track, 35669 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-35669, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-35669, default 35669): Using default value 35669 Command (m for help): p Disk /dev/sdb: 293.3 GB, 293389467648 bytes 255 heads, 63 sectors/track, 35669 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 35669 286511211 83 Linux
The above process creates a linux partition the same size as the disk, however we need to change the type from linux to Linux LVM as this partition will be part of Logical Volume Management (LVM)
Whilst still in the fdisk /dev/sdb utility do the following
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): p Disk /dev/sdb: 293.3 GB, 293389467648 bytes 255 heads, 63 sectors/track, 35669 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 35669 286511211 8e Linux LVM Command (m for help):
After the partition type has been changed use the w command to write the partition table to the disk.
Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
We now need to prepare the disk for use in LVM by using the pvcreate command
pvcreate /dev/sdb1
Physical volume "/dev/sdb1" successfully created
Now in this example we are going to extend an existing volume group to incorporate this new partition. You could however create a new VG and add it to that.
Use the vgdisplay command to see the existing volume groups
vgdisplay
--- Volume group --- VG Name system System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 7 VG Access read/write VG Status resizable MAX LV 0 Cur LV 6 Open LV 6 Max PV 0 Cur PV 1 Act PV 1 VG Size 136.48 GB PE Size 4.00 MB Total PE 34940 Alloc PE / Size 16896 / 66.00 GB Free PE / Size 18044 / 70.48 GB VG UUID Xcgf7x-W6FJ-OMPa-0j21-XIdt-NLFz-PshfWe
We are going to add /dev/sdb1 into the existing VG called system by using the vgextend command
vgextend system /dev/sdb1
Volume group "system" successfully extended
Use the vgdisplay command again to view the statistics for the VG. Check the Free row to ensure the free disk space in the VG has increased as shown below.
vgdisplay
--- Volume group --- VG Name system System ID Format lvm2 Metadata Areas 2 Metadata Sequence No 8 VG Access read/write VG Status resizable MAX LV 0 Cur LV 6 Open LV 6 Max PV 0 Cur PV 2 Act PV 2 VG Size 409.72 GB PE Size 4.00 MB Total PE 104888 Alloc PE / Size 16896 / 66.00 GB Free PE / Size 87992 / 343.72 GB VG UUID Xcgf7x-W6FJ-OMPa-0j21-XIdt-NLFz-PshfWe
In this case we want to use the capacity of the new partition to create a new logical volume. This can be achieved by using the lvcreate command
lvcreate -L 293G -n logs system
Logical volume "logs" created
This command creates a 293GB logical volume called logs in the system VG
We now need to create a filesystem on the LV as follows
mkfs.ext3 /dev/system/logs
mke2fs 1.38 (30-Jun-2005)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
38404096 inodes, 76808192 blocks
3840409 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=79691776
2344 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, 11239424, 20480000, 23887872, 71663616
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 35 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
This creates an ext3 filesystem on the logs LV
Now all we have left to is mount the new filesystem, in this case on an existing directory called logs
mount /dev/system/logs /logs
Lastly don't forget to edit /etc/fstab so that this filesystem is mounted on boot