Logical Volume Management

Create Mirrored Volume

Purpose

To mirror two 4TB disks.

Steps

[root@natasha ~]# pvcreate /dev/sd[b-c]
  Physical volume "/dev/sdb" successfully created.
  Physical volume "/dev/sdc" successfully created.

[root@natasha ~]# vgcreate DATA /dev/sd[b-c]
  Volume group "DATA" successfully created

[root@natasha ~]# lvcreate -m1 -L 3.63T -n mirror1 DATA
  Rounding up size to full physical extent 3.63 TiB
  Logical volume "mirror1" created.

Fix excluded by filter

[root@natasha ~]# wipefs -a /dev/sdb
/dev/sdb: 8 bytes were erased at offset 0x00000200 (gpt): 45 46 49 20 50 41 52 54
/dev/sdb: 8 bytes were erased at offset 0x3a3817d5e00 (gpt): 45 46 49 20 50 41 52 54
/dev/sdb: 2 bytes were erased at offset 0x000001fe (PMBR): 55 aa
/dev/sdb: calling ioctl to re-read partition table: Success

Grow logical volume

Purpose

A couple small servers I had built using the vmware defaults started to run out of space, and everytime this happens I fail to record the steps and have to look up a refresher. This time I will record it.

Steps

NOTE: The following uses defaults. If you need to look up specific information on your system, use vgdisplay and lvdisplay.

• Create a new partition on the disk

fdisk /dev/sda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p

Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000606ed

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    20971519     9972736   8e  Linux LVM

Command (m for help): n
Partition type:
   p   primary (2 primary, 0 extended, 2 free)
   e   extended
Select (default p):
Using default response p
Partition number (3,4, default 3):
First sector (20971520-41943039, default 20971520):
Using default value 20971520
Last sector, +sectors or +size{K,M,G} (20971520-41943039, default 41943039):
Using default value 41943039
Partition 3 of type Linux and of size 10 GiB is set

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

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

• Run partprobe so kernel knows of new partition.
• Add the partition as a physical parition for LVM

pvcreate /dev/sda3

• Add the new physical volume to the volume group

vgextend centos /dev/sda3

• Extend the logical volume

lvextend /dev/centos/root /dev/sda3

VMWare Specific

To detect a resized disk running on VMWare, you need to scan the scsi controller before expanding the volume.

echo 1 > /sys/class/scsi_device/0\:0\:0\:0/device/rescan