topic Mirroring an Array in Operating System - HP-UX

Mirroring an Array

Harvey Beliveau — Tue, 26 Jun 2001 14:57:56 GMT

Hi All:

I'm sure this is probably a simple question, however, being in a position of not having done it before and only having one chance to do it right, I thought it best to ask to be sure.

I have an VA 7100 currently configured at RAID 0 on the first controller. Tomorrow I will be mirroring everything over to the second controller, and I want to make sure that goes very smooth (I actually have two of them to configure). What's the best and/or recommended method of doing so? I'd prefer to have a direct script to do it instead of via SAM, as that way it's something that I have on file for future use (every now and then these types of situations come up).

Looking at another script I have (which is used to mirror a boot drive), I'm guessing the following should be pretty close, but as I said, I want to be sure.

pvcreate -B /dev/rdsk/c0t8d0
vgextend /dev/vg01 /dev/dsk/c0t8d0
lvextend -m 1 /dev/vg01/lvol1
lvextend -m 1 /dev/vg01/lvol2
lvextend -m 1 /dev/vg01/lvol3

Obviously updating this with the correct device and volume groups/logical volumes.

I appreciate your assistance and guidance!

Harvey

Re: Mirroring an Array

John Palmer — Tue, 26 Jun 2001 15:06:05 GMT

Pretty much right apart from the fact that you don't need the -b flag on pvcreate as the disk will not be bootable.

Depending on what disks you have in your volume group, you may want to ensure that the mirrors go where you expect by explicitly naming the disk(s) to lvextend:-

lvextend -m 1 /dev/vg??/lvol? /dev/dsk/?????

Regards,
John

Re: Mirroring an Array

Bill McNAMARA_1 — Tue, 26 Jun 2001 15:10:22 GMT

It looks okay in principle..
You might want to look at physical volume groups if you have lots of luns to mirror.
See the man on vgcreate section PVGs.
Physical volume groups allow you to make sure that your mirror is located accessing through a different controller so that you don't have to worry about mirroring through the same controller by accident or even mirroring across the same array introducing single points of failure.

I'm not sure on the VA disk system and perhaps you'll get more input in hte storage forum but on an autoraid for example mirroring your lun on the same array wouldn't make sense since the lun is distrubuted across all disks in any case.. if your VA array is fixed disk approach raid mirroring across one VA to another using PVGs is fine.. mirroring within the same enclosure is just going to cost you disk space if it is already raid protected and accessable from the other controller via lvm alternate links.. vgextend vgname /dev/dsk/ctd alternate.

Bill