How to enforce device file names ? 1

[hoinz]

Hello,

how can we force HP-UX to let us choose the device file names for tape drives?
We are running a backup server (Legato Networker, but that shouldn't matter for this question) on an HP-UX cluster with two nodes, version 11.23 on IA64. The software relies on device names being the same, no matter on which of the two nodes it is running.
When adding new drives, we let HP-UX do the naming, and, not surprising, names are different on the two nodes.
How could we change that?

regards

 

[KenCunningham]

Hi hoinz. Probably too simplistic, but could you not just link the unwanted device name to the one you want to use?

I don't mind people who aren't what they seem. I just wish they'd make their mind up.

 

[hoinz]

Thanks Ken,

Well, I never tried linking device files; not sure about this.
Does the Unix kernel store information about device names?
It seems links for device files aren't widely used in the Unix community, and I wonder why?
Or am I missing something?

But in any case, it might be worth a try, giving Legato just links instead of device files.
It's a bit complicated, because some device files, let's say /dev/rmt/c68t0d2BESTnb, exist on both nodes, and it's drive1 in libraryA on one node1, and drive3 in libraryB on node2. But choosing new names on both nodes would resolve it.

Probably we will continue testing tomorrow; for now we are happy with our backup software running on one cluster node.

I'll keep you informed!

regards

 

[KenCunningham]

hoinz - good luck and thanks for keeping us informed. It will be interesting to see what transpires.

I don't mind people who aren't what they seem. I just wish they'd make their mind up.

 

[Martin999]

Best solution ...

Use links eg. /dev/link/TAPE1 (which links to say /dev/rmt/0mnb)etc...

So you then control what is what, and, if the device files change (say a SAN change occurs) instead of recreating the jukebox, just swap the links round.

You can force hp-ux to reorder the actual devices, but this is time consuming and much more complex then using links.

Martin

 

[daFranze]

>> You can force hp-ux to reorder the actual devices, but this is time consuming and much more complex then using links.

I have seen this in the hp Service Guard training; it was a little bit complex.
I agree, use links (which are a little bit frowned upon in hp but widelz spread in Solaris) for an easy going

Best Regards, Franz
--
UNIX System Manager from Munich, Germany

 

[hoinz]

Thank you all for your help;
links could solve part of our problems.

I hadn't told you that we added two SCSI jukeboxes, not just single drives.
And so, besides new device files for tape drives, we also got new device files for jukebox robotics. And no surprise, they differ, too.
And now we found out that Legato Networker calls tape drives by device file name, whereas it calls robotics by SCSI id, and there is no way around it.

So the question I asked was partly wrong. Regarding robotics it's more about SCSI id than about file names.
We can see two possible solutions now:

1) Re-arrange SCSI ids, or rather let a consultant do it. I suppose our knowhow isn't sufficient. We are just migrating from Tru64 Unix to HP-UX, and haven't got in-depth training.

2) For tape drives use links, as suggested. For robotics add a script to the Networker cluster package, that will, on startup, adjust jukebox configuration data.
This seems feasible. However we'll have to find out if this solution is fully supported by Legato. It wouldn't help much, if we got it to run for now, bet when there was a problem later, Legato support suspected that it was due to our unsupported dirty tricks.

regards

 

[KenCunningham]

Wow, hoinz, that's some complicated arrangement. Best of luck with it.

I don't mind people who aren't what they seem. I just wish they'd make their mind up.

 

[yai]

remember: hard links to device files show up as device files in e.g. "ioscan -fnCtape" command. softlinks don't. Legato might not follow softlinks, so hard links are always a good choice.