lock disk questions - changing disk paths

[mattman]

I have a HPUX 11.23 vpar running Serviceguard A.11.18.  This previously was setup as a 2 node cluster but the second half was decommissioned and it was made a single node.

We have a requirement to move SAN and will need to plug in new fiber cables, resulting in changing disk paths. My concern is the current lock disk is configured with the target name. What happens when that target name goes away?

We have dual port FC cards, so the plan is to unplug existing cable, plug in new cable, rescan, vgreduce the old paths, vgextend the new paths.  Repeat for the 2nd port.

We've done this will no outage on a standalone server, but I'm not so sure its possible with lock disks in play.

Can I change a lock disk on the fly without halting the cluster?

[Duncan Edmonstone]

First off, Serviceguard 11.18 is out of support - the last an only supported version on HP-UX 11.23 is Serveicguard 11.19.

Regarding the cluster lock disk - if the cluster is already started, the only time when the software would attempt to access the lock disk would be in a situation where the cluster cannot get to quorum. In a single node cluster that can never happen, so the software will never need to access the cluster lock disk. You will probably get warning messages in your syslog about no longer being able to access that path, but you can just ignore those if you wish until you have the chnace to shutdown the cluster and make the necessary chnages.

[mattman]

Thanks for the reply, yes this system is out of support, however its running a custom app that would be expensive to re-engineer for later OS & hardware.  Money the customer doesn't want to spend until they absolutely have to.

It sounds like this will be a non-issue for the single node, which is great news.  How about the 2 node cluster with 11.31?  Are there any gotcha's I need to be aware of pertaining to the lock disks?

[Mike_Chisholm]

For Serviceguard 11.20 on HP-UX 11.31, cluster lock parameters can generally be changed online. The document you want to look at is the Managing Serviceguard manual. It will probably answer all your questions. Specifically, see section "Updating the Cluster Lock Disk Configuration Online", but you can just search for "lock disk" and read up on the other details in various sections of the manual.

https://support.hpe.com/hpsc/doc/public/display?sp4ts.oid=5199828&docLocale=en_US&docId=emr_na-c05323984

If you are running a version of Serviceguard earlier than 11.20 on HP-UX 11.31 you should strongly consider upgrading.

[mattman]

---

@Mike_Chisholm wrote:

For Serviceguard 11.20 on HP-UX 11.31, cluster lock parameters can generally be changed online. The document you want to look at is the Managing Serviceguard manual. It will probably answer all your questions. Specifically, see section "Updating the Cluster Lock Disk Configuration Online", but you can just search for "lock disk" and read up on the other details in various sections of the manual.

https://support.hpe.com/hpsc/doc/public/display?sp4ts.oid=5199828&docLocale=en_US&docId=emr_na-c05323984

If you are running a version of Serviceguard earlier than 11.20 on HP-UX 11.31 you should strongly consider upgrading.

---

Unfortunately, this system is running Serviceguard 11.18.  This is the main reason for my concern with these lock disks, I do not have this option. 

I was hoping this would be a seemless change.  Please clarify something for me, if the cluster lock disk is /dev/dsk/disk20, and the path is /dev/dsk/c20t0d0, if that path changes to say c30t0d0 but the disk remains disk20, nothing should change with the cluster right?