[linux-lvm] Cannot create a logical volume

[linux-lvm] Cannot create a logical volume

[Vikas]

Objective: Be able to take snapshots of XEN disk images for backup.

Problem: lvcreate is failing

The environment:

[root@localhost ~]# pvscan
  PV /dev/md3   VG gt_vg   lvm2 [909.91 GB / 909.91 GB free]
  Total: 1 [909.91 GB] / in use: 1 [909.91 GB] / in no VG: 0 [0   ]

[root@localhost ~]# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "gt_vg" using metadata type lvm2

[root@localhost ~]# vgdisplay gt_vg
  --- Volume group ---
  VG Name               gt_vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  7
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               909.91 GB
  PE Size               32.00 MB
  Total PE              29117
  Alloc PE / Size       0 / 0
  Free  PE / Size       29117 / 909.91 GB
  VG UUID               j4aEP0-PCwG-Qyub-DCxw-aVVp-VyCK-EkZUsN

[root@localhost ~]# lvcreate -L 5G -n data gt_vg
  Not enough PVs with free space available for parallel allocation.
  Consider --alloc anywhere if desperate.

Any feedback would be very much appreciated,

Thanks for your time,

-- 
Vikas

Re: [linux-lvm] Cannot create a logical volume

[Jaroslav Stava]

Vikas wrote:
> Objective: Be able to take snapshots of XEN disk images for backup.
>
> Problem: lvcreate is failing
>
> The environment:
>
> [root@localhost ~]# pvscan
>   PV /dev/md3   VG gt_vg   lvm2 [909.91 GB / 909.91 GB free]
>   Total: 1 [909.91 GB] / in use: 1 [909.91 GB] / in no VG: 0 [0   ]
>
> [root@localhost ~]# vgscan
>   Reading all physical volumes.  This may take a while...
>   Found volume group "gt_vg" using metadata type lvm2
>
> [root@localhost ~]# vgdisplay gt_vg
>   --- Volume group ---
>   VG Name               gt_vg
>   System ID
>   Format                lvm2
>   Metadata Areas        1
>   Metadata Sequence No  7
>   VG Access             read/write
>   VG Status             resizable
>   MAX LV                0
>   Cur LV                0
>   Open LV               0
>   Max PV                0
>   Cur PV                1
>   Act PV                1
>   VG Size               909.91 GB
>   PE Size               32.00 MB
>   Total PE              29117
>   Alloc PE / Size       0 / 0
>   Free  PE / Size       29117 / 909.91 GB
>   VG UUID               j4aEP0-PCwG-Qyub-DCxw-aVVp-VyCK-EkZUsN
>
> [root@localhost ~]# lvcreate -L 5G -n data gt_vg
>   Not enough PVs with free space available for parallel allocation.
>   Consider --alloc anywhere if desperate.
>
> Any feedback would be very much appreciated,
>
> Thanks for your time,
>
>   
AFAIK this message should be seen only when trying to create a mirrored
or striped lv.

Post at least the log of -vvv run, so we can guess why this is happening.
Posting extended lvm info could be helpful too - try lvmdump.

Regards,

Jaroslav Stava

Re: [linux-lvm] Cannot create a logical volume

[Milan Broz]

Jaroslav Stava wrote:
>> [root@localhost ~]# pvscan
>>   PV /dev/md3   VG gt_vg   lvm2 [909.91 GB / 909.91 GB free]
>>   Total: 1 [909.91 GB] / in use: 1 [909.91 GB] / in no VG: 0 [0   ]

...
>> [root@localhost ~]# lvcreate -L 5G -n data gt_vg
>>   Not enough PVs with free space available for parallel allocation.
>>   Consider --alloc anywhere if desperate.
>>
>> Any feedback would be very much appreciated,
>>
>> Thanks for your time,
>>
>>   
> AFAIK this message should be seen only when trying to create a mirrored
> or striped lv.
There is another possible problem:

Is the PV allowed to allocate any extents?

Please check "pvdisplay /dev/md3" - there should be
  Allocatable           yes

If not, allow allocation on the PV: "pvchange -x y /dev/md3"
and try lvcreate again.

That error message is misleading it this situation...

Milan
--
mbroz@redhat.com