mirrorvg while app is running

[jtlinksys]

can I mirrorvg the rootvg while the system and apps are up and running without disrupting the users?
I would like to get the mirroring done now, then reboot after-hours.

 

[hirschaj]

Absolutely, mirroring can be done on the fly while the system is up and apps are running.


Jim Hirschauer

http://www.aixexpert.com

 

[p5wizard]

It does put some strain on LVM, so on a heavily loaded system, syncvg during off hours might be more suited...

But for a rootvg, yes go ahead.

Note: what AIX version/ml are you running? I heard there was an issue on syncvg on 5300-00 - Guy I know crashed a system while syncvg-ing rootvg after mirroring...

I'm on 5300-02 and 5200-05 and haven't encountered the problem...





HTH,

p5wizard

 

[jtlinksys]

Im running 5100-04.
One other question, I ran the bosboot and bootlist then rebooted.
IS quorum supposed to be off? (Notice Quorum is 1)
If thats the case, then why is a reboot necessary if quorum is turned off by default when mirror vg is run?

root@iris # lsvg rootvg
VOLUME GROUP: rootvg VG IDENTIFIER: 000f7d3d61ed6302
VG STATE: active PP SIZE: 16 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 1084 (17344 megabytes)
MAX LVs: 256 FREE PPs: 684 (10944 megabytes)
LVs: 9 USED PPs: 400 (6400 megabytes)
OPEN LVs: 8 QUORUM: 1
TOTAL PVs: 2 VG DESCRIPTORS: 3
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 2 AUTO ON: yes
MAX PPs per PV: 1016 MAX PVs: 32
LTG size: 128 kilobyte(s) AUTO SYNC: no

Thanks for the help...

 

[hirschaj]

Yes, quorum is supposed to be turned off, but for the change to take effect the VG must varyoff and varyon which requires a reboot for rootvg. The command for manually turning off quorum checking is....

chvg -Qn rootvg


Jim Hirschauer

http://www.aixexpert.com

 

[jtlinksys]

Thanks hirschaj,

So if you run the command chvg -Qn rootvg to turn off quorum, its not actually off until the vg is varied off/on which is a reboot?

 

[hirschaj]

That is correct.


Jim Hirschauer

http://www.aixexpert.com

 

[p5wizard]

your quorum is already turned off, it is set to 1, and you have 3 VG descriptors areas on 2 PVs.

On a two disk VG, one of the disks has 2 VGDAs, the other has just 1 and quorum is set to 2 when on and 1 when off

quorum on ==> value is (#VGDAs/2)+1
if one of the disks fail you are left with 1 or 2 out of three VGDAs and depending on which of the disks failed, your VG would stay up (50/50 chance)

quorum off ==> value is always 1 - doesn't matter how many PVs in the VG
if one of the disks fail you are left with 1 or 2 out of three VGDAs and your VG would stay up regardless of which of the 2 disks failed.

Now you just need to reboot in order to force a varyoffvg/varyonvg to activate the 'no quorum' rule.



HTH,

p5wizard

 

[jtlinksys]

Thanks for the input folks - very helpful.

Not to beat a horse even more, but I beleive that Quorum was already set to 1 (no-quorum) before I ran the mirrorvg.
Does this mean that the reboot was un-needed?

 

[hirschaj]

That is possible, but if it were me I would want to make sure quorum checking was really turned off and get that reboot in. But that is your call.


Jim Hirschauer

http://www.aixexpert.com