topic Strict allocation policy problem in Operating System - HP-UX

Strict allocation policy problem

dictum9 — Wed, 28 Jun 2006 10:42:25 GMT

Running into this when mirroring a logical volume, what could be the case? Has the original been created with the strict allocation policy? Can this be fixed?

sbapc1:/#: lvextend -m 1 /dev/vg00/lvol8 /dev/dsk/c0t4d0
lvextend: Not enough free physical extents available.
Logical volume "/dev/vg00/lvol8" could not be extended.
Failure possibly caused by strict allocation policy

<10 Points>

Re: Strict allocation policy problem

A. Clay Stephenson — Wed, 28 Jun 2006 10:48:41 GMT

The problem is that while you may have enough total free extents to allow the LVOL to be extended there are not enough free extents on separate physical volumes to ensure that all the extents are mirrored on separate PV's. This is actually a good thing because it prevents a single disk failure from causing the loss of data. You can "fix" the problem by using lvchange to disable the strict allocation policy but that is really not something that you want to do. With strict allocation disabled, mirroring does little good.

Re: Strict allocation policy problem

Ivan Ferreira — Wed, 28 Jun 2006 10:50:43 GMT

You can use lvchange -s to set the allocation policy. Just remember then strict policy set to yes is recommended for data availability.

Please post the output of vgdisplay -v vg00.

Re: Strict allocation policy problem

Ninad_1 — Wed, 28 Jun 2006 11:13:16 GMT

You asked
>> Has the original been created with the strict allocation policy?
Can you tell what you are doing ? Is the volume lvol8 already mirrored ? [ lvdisplay -v /dev/vg00/lvol8 | grep -i mirror ]

The message indicates that disk having at least one of the mirror copy does not have enough free blocks. But mu question is if you already have a mirror what are you trying to do with the command you have posted ?

Regards,
Ninad

Re: Strict allocation policy problem

Darrel Louis — Wed, 28 Jun 2006 11:14:45 GMT

Hi,

I assume that the disks are identical.
It's not wise do disable strict allocation policy.
Can you check with vgdisplay -v vg00 and lvdisplay -v /dev/vg00/ the status.

Darrel

Re: Strict allocation policy problem

Steven E. Protter — Wed, 28 Jun 2006 11:18:15 GMT

Shalom,

Mirroring is useless when you mirror the content to the same drive.

The purpose of mirroring is to not lose data or system availability when a single disk fails.

If a logical volume called lvol3 (usually root) is on disk /dev/dsk/c0t0d0 and you make a mirror copy on /dev/dsk/c0t0d0 you have essentially wasted the disk space and not improved reliablity at all.

vgdisplay /dev/vg00

perhaps

vgdisplay -v /dev/vg00

Come up with a plan to redo all of your mirroing so that the logical volume you mirror ends up with the mirror copy on a different disk, perferably a different controller, eg c1 versus c0

SEP

Re: Strict allocation policy problem

dictum9 — Wed, 28 Jun 2006 13:08:27 GMT

It looks like the problem is that that
logical volume in question is location on 2
different PVs. Even though I have enough
physical extents, I cannot mirror it.

Re: Strict allocation policy problem

Albert_31 — Wed, 28 Jun 2006 20:22:36 GMT

Hello etc,

does the lvdisplay show the allocation policy as PVG-strict/strict.

Then just give the
# lvextend -m 1 /dev/vg00/lvol8
LVM will ensure that the mirroring is proper.

else post the lvdisplay /dev/vg00/lvol8

regards

Albert

Re: Strict allocation policy problem

SGUX — Thu, 29 Jun 2006 01:59:54 GMT

Check if the PVG-strict allocation policy is set (man lvcreate, option -s). If so you need to have the file /etc/lvmpvg where the PVG (physical volume groups) are defined. see "man lvmpvg"
What i did a while ago is the following;
- break mirrors to free a disk
- use pvmove to copy LE to the free disk till you have the extends free you need for extending lvol8 (in your case)
- extend lvol8
- use pvmove to copy the LE back to the first PV in the VG
[ optional: create PVG ]
- recreate the mirrors