Quorum & VGDA on for rootvg

[stephnane]

Hi,

Yesterday, my AIX 5.2 server has stopped because hdisk0 was crashed but it was mirrored with hdisk1. I've seen problems on it (hdisk0) before, but I didn't unmirror rootvg, I was thinking that if it crashed, the other one will permit to work.

Question :
- How are the VGDA on hdisk0 and hdisk1 if they are mirrored for rootvg ? How can I see this ?

Tks

 

[p5wizard]

By default, a two-PV volume group has 3 VGDA's. One disk has just one, the other has 2 VGDA's

So a disk crash on a two-PV mirrored rootvg would lead to a system crash 1 out of 2 times. That is because the quorum rule states that at least half of the VGDAs needs to be online (half + one) in order to keep the VG active when a disk fails.

For that type of mirroring (two disk mirrored rootvg e.g.) , you can disable the quorum rule, i.e. set the quorum value to 1. The VG stays online until the last disk fails. (See smitty chvg).

But you need to varyoff/varyon after disabling quorum rule in order for it to become effective; So for rootvg, you need to shutdown/reboot.




HTH,

p5wizard