LVM and VxVM

booting with or without quorum?

 
Michael_325
Occasional Contributor

booting with or without quorum?

Greetings All,

My understanding that quorum is met when 51% of the disks in a volume group are present. If the boot disk is mirrored, I want the system to boot even if one of the mirrors in vg00 is unavailable. Therefore I should modify the AUTO file on the boot disks to allow the system to boot even if vg00 does not meet the quorum during the boot process.

With that in mined, my question is this correct technical thing to do or is not and why/why not? As I have heard it is very dangerous to setup the system to boot without quorum.

Regards
Michael

11 REPLIES 11
Pete Randall
Outstanding Contributor

Re: booting with or without quorum?

Michael,

In the case of a mirrored boot disk, this *IS* the recommended way. Use the mkboot command to update the AUTO file:

mkboot -a "hpux -lq" /dev/rdsk/cNtNdN



Pete

Pete
Sridhar Bhaskarla
Honored Contributor

Re: booting with or without quorum?

Hi Michael,

If you are sure that the disk missing is only the mirror, then you can bring up the VG without quorum. Most of the admins tend to keep only two disks with each mirror to another so that booting with -lq option wouldn't be an issue and it is recommended.

The issue will come where you have logical volumes that don't have mirrors but spread across multiple disks in vg00 and if one of the disks fail.

-Sri
You may be disappointed if you fail, but you are doomed if you don't try
Steven E. Protter
Exalted Contributor

Re: booting with or without quorum?

You certainly don't want to run for a long time without a quorum.

But, quorum rules come from back when you needed larger numbers of small disks to have enough disk space.

Now most servers have a couple of 73 GB boot disks local if that.

If one drive fails, you don't have a quorum. To get your system going while you wait for HP Hardware to get you a new hot swap/pluggable drive, its just fine to boot -lq

SEP
Steven E Protter
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Michael_325
Occasional Contributor

Re: booting with or without quorum?

Thank you all for the quick replies this is just wonderful.

In my case the boot disks has only vg00 on them and I got them configured to boot without quorum. I would like to keep it that way for as long as possible. So if one disk failed and the system had to reboot I do not have to be present to allow the system to boot to the other disk.

Regards,
Michael
Patrick Wallek
Honored Contributor

Re: booting with or without quorum?

If you want to make sure that your machine will reboot without one of the root drives you also need to verify that AUTOBOOT and AUTOSEARCH are both set to ON. You can run the 'setboot' command without any options to see what your settings are.

This comes into play if your primary drive is dead. With those ON the machine should search and boot from the other boot drive.

There has been a recent thread where this is not behaving as it should be on D series boxes.

A. Clay Stephenson
Acclaimed Contributor

Re: booting with or without quorum?

It's actually more important that -lq be set on the primary drive because in this case the box would not boot unassisted if the alternate drive were dead. It's really not so important to set it on the alternate because you are not going to be booting that much anyway. The main purpose of mirroring is to allow you to continue operatiosn with a failed boot drive -- and even replace the boot drive "on the fly" is the drives are hot-plug.
If it ain't broke, I can fix that.
Pete Randall
Outstanding Contributor

Re: booting with or without quorum?

Michael,

As you said, you've "configured to boot without quorum. I would like to keep it that way for as long as possible." This, I'll repeat, is the way it should be. There were a few misleading answers about "you can boot anytime without quorum", "you shouldn't run for long without quorum", etc. You want to set your primary drive up with "hpux -lq", autoboot and autosearch (thanks Patrick), so that it will boot without manual intervention. Once it does boot, you need to detect and correct the problem immediately.


Pete

Pete
Michael_325
Occasional Contributor

Re: booting with or without quorum?

Pete & Patrick,

Yes indeed and as you see from the setboot output that Autoboot as well as Autosearch are enabled and the â hpux â lqâ is set for both mirrored disks. And I would like to keep it this way for the life of the system.


lifcp /dev/rdsk/c1t0d0:AUTO -
hpux -lq
lifcp /dev/rdsk/c2t2d0:AUTO -
hpux â lq

setboot
Primary bootpath : 0/0/1/1.0.0
Alternate bootpath : 0/0/2/0.2.0

Autoboot is ON (enabled)
Autosearch is ON (enabled)

Thanks a lot for your feedba
Sridhar Bhaskarla
Honored Contributor

Re: booting with or without quorum?

Michael,

I didn't see the misleading answer of "you can boot anytime". If we are talking about only this thread, then the most matching sentence is mine saying that you can boot without quorum *if you are sure that the missing drive is the mirror*. If that is not the case you would be booting into LVM maintenance mode where you will try to fix your bad disk.

But I would like to clarify one thing on setting this only on primary path. I for one simply hate to see the system coming up always on only one disk. Whenver I get a chance, I try to boot the system from the other disk to ensure that my mirrors are good. So, you may see any disk as the primary. So, it is better to configure -lq on both the disks.

And with auto-search and auto-boot, a regular checking of your 'setboot' output is also a good practice.

-Sri

You may be disappointed if you fail, but you are doomed if you don't try