====== General guide for LVM ======

===== Prepare new disk/VolumeGroup/Logical Volume =====

Add disk/LUN to server. Have a look at [[rescan_scsi_bus|Rescan SCSI bus]] for scanning the SCSI bus online. Alternative reboot the server.

Prepare PV's with
  pvcreate /dev/<device>
For FC LUN's use /dev/mapper/mpath<x> according to Red Hat DM Multipath Configuration & Administration

Create VG
  vgcreate <vgname> -s <Physical Extent size> <path to PV>
  
Create LV
  lvcreate --name <lvname> --size <xx>G <vgname>
  
Create filesytem

EXT FS:
   mkfs.ext4 -F -b 4096 /dev/<vgname>/<lvname>
Depending on distribution use relevant ext2/ext3/ext4 file system type.

XFS FS:
   mkfs.xfs /dev/<vgname>/<lvname>
===== Resize existing Logical volume =====

Extend the disk on the underlying infrastructure (SAN LUN / Virtulization platform)

Make OS detect the changed disk size

  echo 1 > /sys/block/<device>/device/rescan

Where the <device> paramter is the physical disk eg. sdb

Resize Physical Volume
   pvresize /dev/<device>
   
If LUN is under multipath:
   multipathd resize map <multipath_device>
   
Where <multipath_device> is mpath<x> or wwid depending on multipath configuration.

Extend Logical Volume
    lvextend -l 100%VG <lvname>
check man lvextend for further options

Extend filesytem which resides on Logical Volume

EXT FS:
   resize2fs /dev/<vgname>/<lvname>

XFS FS:
    xfs_growfs /dev/<vgname>/<lvname>

[[https://access.redhat.com/kb/docs/DOC-9855]]

===== Resize swap on Logical volume =====

Determine which LV is in use by swap space

  grep swap /etc/fstab
  Example of output:
  /dev/mapper/VolGroup00-LogVol01 swap                    swap    defaults        0 0

Disable swap:
  
  swapoff /dev/mapper/VolGroup00-LogVol01

Resize swap space.

In this example swap spaze is adjusted to 4GB.

  lvresize -L 4G /dev/mapper/VolGroup00-LogVol01

Setup swap area on LV

  mkswap /dev/mapper/VolGroup00-LogVol01

Enable swap space again

  swapon /dev/mapper/VolGroup00-LogVol01
  
Verify with top or /proc/swaps:
  
  top

output:\\
top - 13:32:16 up 14 min,  2 users,  load average: 0.22, 0.08, 0.02\\
Tasks: 138 total,   2 running, 136 sleeping,   0 stopped,   0 zombie\\
Cpu(s):  4.2%us,  1.5%sy,  0.0%ni, 93.0%id,  1.1%wa,  0.0%hi,  0.1%si,  0.0%st\\
Mem:   3925256k total,   486996k used,  3438260k free,   102092k buffers\\
//**Swap:  4194296k total**//,        0k used,  4194296k free,   118264k cached

  cat /proc/swaps
  Filename                                Type            Size    Used    Priority
  /dev/dm-1                               partition       4194296 0       -1