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"boot vmunix -lq": is it safe?

 
Zdenek Precek
Occasional Contributor

"boot vmunix -lq": is it safe?

Hi gurus!

When creating the bootable mirror of the LVM root disk, everybody suggests to change the content of the AUTO file on BOTH physical disks to contain either "boot vmunix -lq" or "hpux -lq" depending on the server architecture.
See e.g. this thread: https://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1100656&hpweb_printable=true

At the same time, the excellent whitepaper here: http://docs.hp.com/en/5991-1236/When_Good_Disks_Go_Bad_WP.pdf discourages to this because of possible data loss (see e.g. "Appendix D, Procedures", "Mirroring the Root Volume on Integrity Servers, step 6.a.)

Why is it unsafe to boot the system ALWAYS with "-lq" ?
4 REPLIES
James R. Ferguson
Acclaimed Contributor

Re: "boot vmunix -lq": is it safe?

Hi:

In my opinion the "possible data loss" should only be if one or more of the logical volumes of vg00 were *not* mirrored. Since I wouldn't configure a system this way, and since I don't want a panic on loss of quorum (as the whitepaper notes), I specify the low quorum in both of my vg00 disks.

Regards!

...JRF...
Torsten.
Acclaimed Contributor

Re: "boot vmunix -lq": is it safe?

The only issue I see is the system boots up fine and you are probably not aware of the missing disk - until the remaining disk fails too.

Hope this helps!
Regards
Torsten.

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Patrick Wallek
Honored Contributor

Re: "boot vmunix -lq": is it safe?

I agree with James. I also always set both of my mirrored boot disks to use the '-lq' option.

James R. Ferguson
Acclaimed Contributor

Re: "boot vmunix -lq": is it safe?

Hi (again):

While Torsten makes a good point; viz "... you are probably not aware of the missing disk - until the remaining disk fails too." I would *still* want a low-quorum enabled in the absence of a *specific* rationale from HP.

My argument is that at least some of the time your hardware monitoring (EMS for example) will alert you to a failure or a degradation in service.

It is possible for the loss of a mirrored boot disk to cause a server crash. If it does, I want the low-quorum enabled so that I can recover availability as soon as possible without manually intervening to reboot.

My comments in this case are directed to non-clustered servers (i.e. no MC/ServiceGuard or other HA product) with only one mirror of the boot disk's logical volumes. Having an HA environment and/or multiple mirrors lessens the desire/need to establish a low-quorum in my opinion. Hence, I think you need to define (for yourself) your environment and your service level agreement requirements in order to make an optimal choice.

Regards!

...JRF...