[CentOS] Can't create mirrored LVM: Insufficient suitable allocatable extents for logical volume : 2560 more required

[Rudi Ahlers]

I'm trying to setup a LVM mirror on 2 iSCS targets, but can't.

I have added both /dev/sda & /dev/sdb to the LVM-RAID PV, and both
have 500GB space.


[root at HP-DL360 by-path]# pvscan
  PV /dev/cciss/c0d0p2   VG LVM        lvm2 [136.59 GB / 2.69 GB free]
  PV /dev/sda            VG LVM-RAID   lvm2 [500.00 GB / 490.00 GB free]
  PV /dev/sdb            VG LVM-RAID   lvm2 [502.70 GB / 492.70 GB free]
  Total: 3 [1.11 TB] / in use: 3 [1.11 TB] / in no VG: 0 [0   ]


[root at HP-DL360 by-path]# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "LVM" using metadata type lvm2
  Found volume group "LVM-RAID" using metadata type lvm2


I can add a single LVM volume:

[root at HP-DL360 by-path]# lvscan
  ACTIVE            '/dev/LVM/root' [10.00 GB] inherit
  ACTIVE            '/dev/LVM/swap' [3.91 GB] inherit
  ACTIVE            '/dev/LVM/data' [120.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol0' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol1' [10.00 GB] inherit
[root at HP-DL360 by-path]# lvcreate -L 10G  LVM-RAID
  Logical volume "lvol2" created

Yet, when I try and add a mirror, I get this:

[root at HP-DL360 by-path]# lvcreate -L 10G -m1 LVM-RAID
  Insufficient suitable allocatable extents for logical volume : 2560
more required
  Unable to allocate extents for mirror(s).



I can create a stripe though:

[root at HP-DL360 by-path]# lvcreate -L 20G -i2 -I64 LVM-RAID
  Logical volume "lvol3" created
[root at HP-DL360 by-path]# lvscan
  ACTIVE            '/dev/LVM/root' [10.00 GB] inherit
  ACTIVE            '/dev/LVM/swap' [3.91 GB] inherit
  ACTIVE            '/dev/LVM/data' [120.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol0' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol1' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol2' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol3' [20.00 GB] inherit



I could even create a large stripe:

[root at HP-DL360 by-path]# lvcreate -L 600G -i2 -I64 LVM-RAID
  Logical volume "lvol4" created
[root at HP-DL360 by-path]# lvscan
  ACTIVE            '/dev/LVM/root' [10.00 GB] inherit
  ACTIVE            '/dev/LVM/swap' [3.91 GB] inherit
  ACTIVE            '/dev/LVM/data' [120.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol0' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol1' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol2' [10.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol3' [20.00 GB] inherit
  ACTIVE            '/dev/LVM-RAID/lvol4' [600.00 GB] inherit
[root at HP-DL360 by-path]# pvscan
  PV /dev/cciss/c0d0p2   VG LVM        lvm2 [136.59 GB / 2.69 GB free]
  PV /dev/sda            VG LVM-RAID   lvm2 [500.00 GB / 180.00 GB free]
  PV /dev/sdb            VG LVM-RAID   lvm2 [502.70 GB / 172.70 GB free]
  Total: 3 [1.11 TB] / in use: 3 [1.11 TB] / in no VG: 0 [0   ]



But, the mirror keeps failing:

[root at HP-DL360 by-path]# lvcreate -L 10G -m1 LVM-RAID
  Insufficient suitable allocatable extents for logical volume : 2560
more required
  Unable to allocate extents for mirror(s).


This is on CentOS 5.5 x64

[root at HP-DL360 by-path]# cat /etc/redhat-release
CentOS release 5.5 (Final)
[root at HP-DL360 by-path]# uname -a
Linux HP-DL360 2.6.18-194.32.1.el5xen #1 SMP Wed Jan 5 18:44:24 EST
2011 x86_64 x86_64 x86_64 GNU/Linux


Does anyone know why this happens?






-- 
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532