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primary OS mirror drive fails and HP-UX will crash?

 
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Adam Garsha
Valued Contributor

primary OS mirror drive fails and HP-UX will crash?

In HP-UX 11.23, if your primary vg00 OS mirror disk fails... is the box supposed to crash? Support says yes... "normal".

Hmm... What? Ha? Can that really be true?

Thanks.
7 REPLIES
Pete Randall
Outstanding Contributor
Solution

Re: primary OS mirror drive fails and HP-UX will crash?

Sure. You're running off that disk. If it goes away, you're going to crash. The point of mirroring is to get the machine back up again with minimal downtime and no loss of data.


Pete

Pete
James R. Ferguson
Acclaimed Contributor

Re: primary OS mirror drive fails and HP-UX will crash?

Hi Adam:

Yes, one should expect a failure in the mirror from which you booted to cause a system crash.

Mirroring is a "high-availablity" strategy, not a "fail-safe" one. You are guaranteed not to lose data and you are guaranteed to be "highly available" insofar as you can expected to be up *almost* all the time. If you can boot and resume normal operations, then you are highly-available, though not always-available.

Regards!

...JRF...
Torsten.
Acclaimed Contributor

Re: primary OS mirror drive fails and HP-UX will crash?

IMHO from the system point of view you have 2 originals - more or less, because the (file) system deals with LVOLS, not with the disk directly.

This assumes you have everything mirrored, of course.

To use a hardware raid (available in current entry class servers by default) makes all this much easier.

Hope this helps!
Regards
Torsten.

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Patrick Wallek
Honored Contributor

Re: primary OS mirror drive fails and HP-UX will crash?

I have to disagree with my counterparts.

If my primary OS disk fails, and it is mirrored correctly, then the server should not crash.

Once the server has been booted, the disk you booted from should be irrelevant. Reads and writes are handled by the kernel and if one disk is dead then you should run off of the other one.

The one caveat to this is swap space. You must make ABSOLUTELY SURE that your primary swap space, usually vg00/lvol2, is mirrored. If it isn't, and the disk containing pri swap fails, then you will have a system crash.

Otherwise you server should keep running.

I would ask for this question to be routed to a level 2 or level 3 support engineer to verify.
Patrick Wallek
Honored Contributor

Re: primary OS mirror drive fails and HP-UX will crash?

I've just done a test....

I have a test server, model A500, running HP-UX 11iv2 (aka 11.23) with mirrored drives for the OS.

I pulled out the primary drive so I am now running on only 1 drive.

If I do a vgdisplay I see the lvols marked as 'stale' and the drive itself is unavailable.

The server stayed up and running though and has NOT crashed. This is the behavior that I expect with mirrored VG00 drives.
James R. Ferguson
Acclaimed Contributor

Re: primary OS mirror drive fails and HP-UX will crash?

Hi (again):

Patrick, my friend, I agree with your premise and your test supports it. I still stand by my comment that "one should expect a failure"...which is different than "there will be..."

Regards!

...JRF...
OldSchool
Honored Contributor

Re: primary OS mirror drive fails and HP-UX will crash?

I recall testing this on L-class boxes w/ 11.0 and it worked just fine....

older K-class boxes did some funny stuff...they didn't crash, but some things broke. and trying to get the bad disk out of the setup was ugly. all the "lv.." commands hung...apparently on exit.