extending FS with PVG-strict/distributed allocation

[Jino PV]

Hi

I have an LV with PVG-strict/distributed allocation policy set. There are 12 disks in that VG an this particular LV is not mirrored./etc/lvmpvg is of 0 byte. In the 12 disks in VG, 6 disks are completely free. I was trying to extend the lv from 30Gig to 60Gig. But its giving me error "not enough space". I would like get your expert opinion on resolving this.
Do you suggest to change the allocation policy? May be to strict?
lvmchange -s y "lv"
or any other easy way?

Also I would like to know is it safe to change the allocation policy on fly. The filesystem is mounted and its a part of cluster.

Thanks

Jino

[Eric SAUBIGNAC · Accepted solution]

Bonjour JINO,

I don't think you need to modify allocation policy. Just fill up /etc/lvmpvg with the 6 completely free devices (man lvmpvg) and you will be able to extend the LV ... if it finally gives less than 65536 extends in this LV.

There is no problem if you change allocation policy on fly : it is "allocation" policy. That's mean allocation policy it used by LVM at creation time, or extension, of the LV, not after. There is no matter if you modify it after creation or extension of the LV.

Regards

Eric

[Jino PV]

Hi Eric

Do you mean to say just create the /etc/lvmpvg file with following entry?

VG /dev/vg03
PVG PVG0
/dev/dsk/c2t0d0
/dev/dsk/c2t0d1
/dev/dsk/c2t0d2
/dev/dsk/c2t0d3
/dev/dsk/c2t0d4
/dev/dsk/c2t0d5
/dev/dsk/c2t0d6
/dev/dsk/c3t0d0
/dev/dsk/c3t0d1
/dev/dsk/c3t0d2
/dev/dsk/c3t0d3
/dev/dsk/c3t0d4
/dev/dsk/c3t0d5
/dev/dsk/c3t0d6
/dev/dsk/c2t0d1
/dev/dsk/c2t0d1
/dev/dsk/c2t0d1


Regards,

[Eric SAUBIGNAC]

Jino,

you spoke of 12 disks, I can see more in your message ... ? Can you control that ? Waiting for your answer, I will continue to suppose that you have 12 dd in this VG.

So the answer to your pervious post is NO.

When you said "In the 12 disks in VG, 6 disks are completely free" I supposed that first 6 dd are full. Right ?

So if you fill /etc/lvmpvg with all the 12 DD, in the same PVG, LVM will try to extend the LV on the 12 DD. It will not find free extends in the first 6 DD, so you will probably get the "not enough space" error message.

Now, if you fill /etc/lvmpvg with the ONLY 6 DD that have full free space, LVM will extend your LV on these only 6 DD. And it will work.

A litlle question : your LV is actually "PVG-strict/distributed" and "etc/lvmpvg is of 0 byte". Though it is not a big problem, how did you raise this situation ?

Eric

[Jino PV]

Hi Eric,

The list of hard disk is not exactly same. I just put some hard disk to show the format. In my case, this particular LV is spread across all first 6 hard disks. And the free PEs in those hard disks vary( Eg. the first hdd have 2PE and second 100PEs).
So if I include only the newly added disk with free PEs in the /etc/lvmpvg, the lvextend should work. Right? or will that still look into the disks where the LV is already present?( If my /etc/lvmpvg is as shown below)

Regarding the /etc/lvmpvg is 0byte:- I just do not know why its so. I joined this compony few months back. So no idea why this LV configured in this allocation policy or why the lvmpvg is 0byte. And I do not see any reason to use pvg here as no mirror is there for LV :)

Regards,

Jino

[Eric SAUBIGNAC]

Jino


--> YES



--> NO. Regardless how your extends are actually allocated, LVM will use, and only use, /etc/lvmpvg to allocate new ones if it is possible: 65535 max extends



--> Probably this LV has been extended several times, with number of extends non-multiple of number of DD.

Eric