quorum..

[benoit Bruckert]

Hi,
My question is simple.
I will move a rack of disk to another room, and I don't want to stop my system.
I have 2 racks in a SAN, one rack is a mirror of the second. I'm using mirror UX.
The question is :
If I break the mirror, and then unplug the previous mirror rack without changing VGs (I.E. that I'll keep all the disks in the vgs), the quorum is active. In my case I have 50% of the disks offline ! Does the vgs are steal active ? Or do I have to vgchange -ay -q n to deativate the quorum on each vg to keep it active ??
The next step is to plug backs disks, and reactivate mirror ? (and change again quorum).
The trouble as I said is that I don't want to stop my server, and I don't want that my vgs are deactivate about a question of quorum ??
This give me another question : On a vg with 2 mirrored disks, if one of them crashed, the quorum is just 50% ! Does the vg stay active ?

[Patrick Wallek · Accepted solution]

Lack of a quorum will NOT cause a VG to deactivate. Say you have a VG with 2 disks and the LVs on one are mirrored to the other and 1 of them goes bad. The VG will still be active. What good would mirror/ux be otherwise?

The only time quorum really comes into play is when you boot the system. If you do not have a quorum on the root VG then the system won't boot unless you use 'hpux -lq' to boot. If it is a non-root VG, then the VG just won't activate if there isn't a quorum.

[S.K. Chan]

The rules about quorum. If your got ONLY 2 disks (mirrored to each other) if one is dead then your quorum check will failed. Onr the other hand if you got say 8 disks, your quorum check will only fail if you got 5 or more disks not responding. The definition for quorum is "..one more than half of your disks in a VG.."
Again this definition does not apply to a 2-disks situation.