Training, more

[sobrique]

Other useful snippets from training:
Engineering mode on clariion disk arrays are enabled by pressing ctrl+shift+f12. The password is 'messner'. However, this is one of these immensely powerful things that can lead to disaster, and mockery from tech support if you screw up.

Also, queue depth on clariion sps has a limitation of about 1600 items. Which is quite a lot. However, if you've just accepted default settings for your LUNs on windows hosts, they each have a queue depth of 32, 64 or sometimes 128. Which means at about 50-100 LUNs, you've got the possibility of overloading your queue. This will trigger SCSI QFULL errors to your hosts. Which is bad. With powerpath, or UNIX, this will lead to a 60 second 'throttle' on the queue, which basically means severely degraded performance.

Without powerpath, the 'throttle' doesn't get managed automatically, so your windows host will just stop queueing at all. This is bad. However, if you're got more than a possible 1600 'queue items' per service processor, you can end up with transient, 60 second 'chugs' on your servers, with a fairly random distribution.

I have a feeling, I've seen this happening. (100 luns x 16 queue depth brings you close to this limit, and I'm fairly sure we're about that mark on our clariion)

Comments

[xarrion.livejournal.com]

Is this common knowledge already, or have you just told the world so that the aforementioned chaos shall spread apace? ;)

Granted, of course, that the number of people who may both a) stumble across your LJ and b) find themselves anywhere near a clariion disk array, is probably not so huge.

[kal-357.livejournal.com]

I know you are talking. I think you are talkig in English. I just don't understand you.