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April 15th, 2010 15:00
Determining workload type (random versus sequential)
I asked this quetion on the Celerra boards and they directed me here. Here's my question: Is there a way to determine the type of workload a lun is performing from the array itself? I know I can do it via Windows Performance Monitor for certain database apps ( if Avg. Disk Bytes / Transfer is significantly higher than 8 KB, for example), but is there analysis I can do on the Clariion to tell me this? Navi Analyser? (if so, how?)
I have a specific customer with several custom applications and no "application developer support" on any of them. So I'm completely in the dark with the apps themselves and I have a feeling the load is sequential, not random, and therefore suffering in its current configuration on the array (mixed random & sequential workloads on the same luns). How do I confirm this (I don't have the luxury of trying and seeing what happens. The case for a change needs to be made first)?
Thanks for any guidance you can provide.
kelleg
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April 16th, 2010 11:00
On the CLARiiON when you open Navisphere - go to the Help and look for Help Contains:
"Analyzing Storage-System Performance using Analyzer"
This should give you a good, overall understanding of what you can monitor on the array using the Navisphere Analyzer package.
glen
driskollt1
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April 27th, 2010 07:00
One of the best ways to tell is to look at how well it's using cache.
Sequential reads and writes make good use of cache.
Hopefully you have Analyzer. if you don't then I don't know what to tell you.
Use the "Performance Detail" graph on a NAR file. Be sure to enable "advanced".
Reads.
Determining sequential reads is easy - Look in Analyzer at a particular LUN and find "Used Prefetches %" - A high % is a good indicator that you're reading sequentially. During backup windows you'll probably see this between 80% - 100%. A low % is a good indicator that it's random.
Read Cache Hit Ratio is Also Good
Writes.
I usually look at the total Write IOs at both the Raid Group and the LUN then compare them. If you have more than one LUN in the RAID Group you'll probably need to do a little basic addition to figure it out. Most of my LUNs are pretty large so they'll occupy a single (usually multipe) RAID Groups.
LUN IO will be MUCH higher than Raid Group IO. I'll see like 1000 IOPs to the LUN and maybe 128 IOPs to the RAID Group..
Also compare write Size of the LUN to the Write Size of the RAID Group. Usually sequential writes will be 512 KB at the RAID Group and MUCH smaller at the LUN.