Problems with LVM quorums between nPars and vPars modes

[Mr Phil Rigby]

I have an RX8640 server with 4 cells. Each cell has 2 internal 146 gb disks. With the RX8640 in nPars mode, I mirrored the factory-installed boot disk, which is in cell 0 at hw path 0/0/0/2/0.6.0 (disk12), to the equivalent disk in cell 2 at hw path 2/0/0/2/0.6.0 (disk18). I defined the disk in cell 2 as the HA alt boot disk. I tested booting in nPars mode from the HA alt path and all worked fine.

I then created two vPars. The first vPar was defined with 0/0/0/2/0.6.0 as its boot disk and the second vPar was defined with 2/0/0/2/0.6.0 as its boot disk. This is how it is recommended to set things up in the vPars manual on the HP web site, ie, each nPar mirror being the root disk of different vPars.

I then changed to vPars mode and ensured that the auto string on the EFI volume of each disk, disk12 and disk18, was set to:

boot vpmon -a

I then rebooted the nPar. Each vPar failed to boot up complaining that the root volume group did not have a quorum of disks. This is quite right since each vPar can only see one of the disks in the original nPar's root vg. I brought the vPars up by running the following from the vPars monitor:

vparload -p ukcsbpd1 -o "-lq"

Now, the problem is that, within each vPar, I want to mirror the vPar's root disk to the other disk that the vPar can access. However, if I do this, I will destroy the mirroring I had defined in nPar mode. If we then had a failure of say the original nPar primary boot disk in cell 0, the nPar would not reboot using the nPar mirror because the vPar mirror config would have destroyed this since it is using the same disk hardware to write the volume group metadata to.

I could just ignore the manual’s instruction and define the nPar mirror on the other disk in cell 0 and then define one vPar so that it can see both these disks. It would anyway if I gave it 0/0/2 as both cell 0’s disks are down this hw path. Is the manual just wrong or does anyone have better suggestions or see any flaws in my work-around?


Thanks,
Phil.

[Torsten.]

"... each nPar mirror being the root disk of different vPars ..."

This will not work.

The mirror must be part of the same vPar.

[Mr Phil Rigby]

Well that is the conclusion I have come to but I am worried because the HP manual HP-UX Virtual Partitions admin guide, part no: T1335-90083 edition 14.1 says the following in chappter 5:-

Autobooting the vPars Monitor and Virtual Partitions

You can setup the Monitor and all virtual partitions to boot automatically at power up. To do this, make sure the following four conditions are met:

1. The hard partitionâ s primary and alternate boot paths point to the boot disks of different virtual partitions. For example, to set the primary and alternate
boot paths at BCH or EFI:

pa pri 0/0/2/0.6.0

pa alt 0/8/0/0.5.0
....
....

So I followed this first condition and implemented the same.

Should I then ignore the manual? If we agree it is wrong, where do I report this to in HP?

Thanks,
Phil.

[Torsten.]

Primary and alternate boot pathes set in firmware (EFI or BCH) has NOTHING to do with LVM mirroring.

This means you should set the boot pathes to different pairs of boot disks.

[Torsten. · Accepted solution]

To say it in different words, you did completely misunderstand what the manual wants to say. There is nothing wrong with the manual.

If you mirror the boot disks in nPar mode, both disk must be in the same vPar.

Now set the systems boot pathes (up to 3 - primary, alternate and HA alternate) to 1 or 2 boot disks of different vPars.

This ensures you are able to boot the vpmon from several different disks.

This only applies if you don't have a mixed configuration.

[melvyn burnard]

As Torsten has already pointed out, this is an incorrect configuration, and you appear to have misunderstood the manuals.
Yes you can mirror the Npar boot disk, but when you turn that Npar int a Vpar, that mirror also needs to go with it's primary into the Vpar. In the Vpar configuration you set the mirror for the Vpar boot disk using the keyword :ALT after specifying the i/o hardware path.
Then you create the next Vpar, with it's own set od boot disks, again specifying the mirror or alternate path in the vparcreate command.
What the manual is telling you is to set the Npar ALTERNATE path to be one of the OTHER Vpar boot disks.
This ensures that if something were to happen to the "primary" Vpar boot configuration you could still boot the other Vpar(s) from the Alternate path which is a DIFFERENT Vpar boot disk, and NOT the moirror of the NPAR

[Mr Phil Rigby]

Thanks Melvyn and Torsten. I've finally got it now. I should never have tried nPar level mirroring. In the end, I cloned disk12 to disk18, made these the boot disks of two different vPars and just set the nPar primary boot path to point at disk12 and the ha alt boot path to point at disk18. I've tested booting in vPars mode using the nPartition primary and alt boot path and all is working fine now. Both my vPars boot automatically each time.

Thanks again for your help guys.

[Mr Phil Rigby]

No need to mirror at nPars level at all.