topic Re: Mirror Disk With Different Size Disks in Operating System - HP-UX

Mirror Disk With Different Size Disks

Andrew Helgeson — Tue, 08 Aug 2006 15:41:59 GMT

I have an rp3440 with 2 internal 34 GB disks and 1 internal 70 GB disk. I'd like to configure the system such that the 2 smaller disks would be mirrored by the larger disk. They would all be in vg00 and I would be able to boot from either the original disk or the larger mirror disk. Is this possible?

Thanks.

Andy Helgeson

Re: Mirror Disk With Different Size Disks

Patrick Wallek — Tue, 08 Aug 2006 15:44:04 GMT

Yes, it is entirely possible as long as your "MAX PE PER PV" value in the VG is large enough to allow the 70GB disk to be fully utilized.

If you have a doubt about that then post or attach the output of 'vgdisplay -v vg00' and we'll let you know for sure.

Re: Mirror Disk With Different Size Disks

IT_2007 — Tue, 08 Aug 2006 15:45:50 GMT

Yes you can mirror and boot it successfully. I have done this before.

Thanks,
Srini

Re: Mirror Disk With Different Size Disks

A. Clay Stephenson — Tue, 08 Aug 2006 15:47:30 GMT

Possibly but probably not. Note that you do not mirror at the disk level but rather at the LVOL level so all 3 disks would have to be in vg00. The problem is that I doubt that you created vg00 with non-default max_pe's value and the VG has been sized to accomate the largest disk detected when the VG was created. This will, in effect, limit your 70GiB disk to 34GiB.

Now, you should whack yourself with a baseball bat because there is never a need for vg00 to be larger than 34GiB so you could have already had a mirrored vg00 using the 2 34GiB disks. vg00 should be for the OS and nothing else.

Re: Mirror Disk With Different Size Disks

James R. Ferguson — Tue, 08 Aug 2006 15:48:08 GMT

Hi Andrew:

Yes, this is possible. LVM mirroring is implemented at the logical volume level, so the different disk sizes mean nothing in this case.

The most important thing to remember is to mirror your logical volumes in the order 'lvol1, lvol2, lvol3...' to match '/stand', primary swap and '/' (root) respectively.

Regards!

...JRF...

Re: Mirror Disk With Different Size Disks

Steven E. Protter — Tue, 08 Aug 2006 15:54:16 GMT

Shalom Andy,

You can mirror root and /stand which are essential to booting.

Because of the size differential, if the second disk is smaller, you can't mirror everything in vg00.

SEP