topic Re: I still don't get it (moving drives) in Operating System - HP-UX

I still don't get it (moving drives)

Marty Metras — Tue, 16 May 2006 10:59:31 GMT

I am trying to move mirrored drives around so they are on different controllers.
I understand the hardware part and which slots the drive belong so the mirrored drives will be using different controllers. I can always backup up the system and do this the hard way. I am looking for another way.

Here is what I still am stuck on.
Each pair of drives are one VG, one LV, and one mount point.
How do break the mirror and/or remove the drive from the VG.
I think I should break the mirror and remove one drive from the system with our losing data or downing the system.
I am looking at "When Good Drives go bad." I stll don't get it.
Marty

Re: I still don't get it (moving drives)

Arunkumar.B — Tue, 16 May 2006 11:09:20 GMT

Hi,

lvreduce -m 0 /dev/vgxx/lvol$ /dev/dsk/cxtydz

#Vgreduce /dev/vgxx /dev/dsk/cxtydz

Remove the drive if its hotspare & connect it to other controller

#insf -H
#pvcreate /dev/rdsk/cxtydz
#vgextend /dev/vgxx /dev/dsk/cxtydz
#lvextend -m 1 /dev/vgxx /dev/dsk/cxtydz

Re: I still don't get it (moving drives)

Steven E. Protter — Tue, 16 May 2006 11:10:01 GMT

Shalom Marty,

Two ways I know to break softwar mirrors.

lvextend -m 0

lvsplit

There are probably others.

I recommend splitting all the mirrors and removing the second copy with lvremove.

Then recreate the mirrors specifying which disk the mirror is going to.

Example the lvol name ls /vg01/lvol1

lvextend -m 1 /vg01/lvol1 /dev/dsk/c1t1d0

Never extend a mirror onto the same controller.

c1 should be extended to c0 or c2 etc.

The nice thing about mirror/ux is you can do this all on the fly.

Letting sam decide where to make the mirror is the normal cause of mirror copies landing on the same disk or controller.

SEP

Re: I still don't get it (moving drives)

Steve Lewis — Tue, 16 May 2006 11:15:52 GMT

If you have a spare disk you could create a 3-way mirror by adding the new disk (that is on the other controller) to your volume group, mirroring all the logical volumes onto it with lvextend -m 2 ... for each logical volume, then
lvreduce -m 1 /dev/vgxx/lvyy /dev/dsk/[one of the disks on the old controller]

That will mean that you never go without a mirrored pair.

Re: I still don't get it (moving drives)

Marty Metras — Tue, 16 May 2006 11:42:11 GMT

If I am understand this correctly I could do this something like this with out moving any moving the drives. Just wait for the mirrod to resync. And use the right hardware addresses.

Break the mirror:
lvreduce -m 0 /dev/vg12/lvol12 /dev/dsk/c10t13d0
Drive is available?

Add another Mirror to vg11 (from above)
lvextend -m 2 /dev/vg11 /dev/dsk/c10t13d0
Now vg11 has a 3 drive mirror?

Remove the unwanter drive from mirror
lvreduce -m 1 /dev/vg11 /dev/dsk/c10t11d0
now vg11 has a 2 drive mirror again?

Marty

Re: I still don't get it (moving drives)

Andrey Tumanov — Tue, 16 May 2006 12:46:37 GMT

If you want to have mirrors accross different controllers you might use PVG-strict allocation policy.

First, you have to create /etc/lvmpvg file that should look like this:

VG /dev/vg01
PVG controller0
/dev/dsk/c0t1d0
/dev/dsk/c0t2d0
PVG controller1
/dev/dsk/c1t1d0
/dev/dsk/c1t2d0

at this point you might want to run vgdisplay -v on your volume group to verify that you PVG are correctly displayed.
then, reduce a mirror with

lvreduce -m 0 /dev/vgXX/lvolXX

change the lvol allocation policy to PVG-strict with

lvchange -s g /dev/vgXX/lvolXX

and add a mirror with

lvextend -m 1 /dev/vgXX/lvolXX

that's all, now you have your lvol mirrored accross different controllers.

Re: I still don't get it (moving drives)

Steve Lewis — Tue, 16 May 2006 14:34:11 GMT

Yes you should mirror across controllers - that normally means a different c number cXtYdZ , so don't put more than one disk on c10. I thought that was why you wanted to move a disk elsewhere.

When you have dropped whichever mirror disk you want to remove from the volume group, you can add it to another volume group instead, where it may be used as a mirror for a disk elsewhere.

For example, suppose you have 8 disks on c10 and 10 disks on c11, you should include some disks from both controllers in each volume group. Just make sure that the disks are the same size, or else things would get more complicated, but not impossible. Something like this:
c10t0d0, c11t0d0, c10t1d0, c11t1d0 in vg01
c10t2d0, c11t2d0, c10t3d0, c11t3d0 in vg02