From: RichGlazier@netscape.net
Date: Sat Feb 08 2003 - 00:08:54 EST
Thank you very much, Ashley, Keith, and Martin, for your on-going dialouge with me. It was very insightful. I think I can summarize by saying, chunck size is really not the issue. All of you directed me away from chunck size, and you were right. The largest performance gain came from simply splitting the load between the controller pair. I had two continious writes going to 2 HSG units, each with a path on the same controller. Aftet I split their paths (using scu> set nexus bus x target x lun x, from the OS) I saw about a 50% performance gain. Here are some excerpts from the respondants:
"Yes 512 is the default (chunk size), we have seen an increase at 2048 and 4192 for the log file size with 4192 being the plateau were any performance increase leveled off."
"In case you have only one LUN on the stripeset - which means only 1
controller services it - maximum perfomance you should normally expect
would be:
~45MB/s read perfomance
~30MB/s write perfomance
~4000iops (50%read/50%write)"
"The absolutely best perfomance we have achieved was ~65MB/s read, 38MB/s
write, ~8000iops - and that was with 12 36GB/s 15k rpm disks, chunksize
the size of oracle database chunks, cache write set to 128, cache read
set to 64, cache timer to 30s."
>Admins,
>
>I have a stripeset that has very large file, continuous writes. The write performance is poor, and I'm wondering if increasing the stripe size (chunck size) would help. Here are the specs:
>
>GS80 connected via switched SAN to EMA1200- Multi Bus Failover HSG80s
>
>Stripeset is made up of 6 72GB, 15K disks, and has a default 256 block chunk size.
>
>The entire dsk is used in a single volume/fileset.
>
>---
>
>Given that this is for writes only, and the writes are large and continuous, should I increase the chunksize of the stripeset, and increase the write block size of the file domain in advfs? What factors do I need to consider when choosing a chunksize (i.e. disk geometry, cylinder, etc.)? The StorageWorks books arn't real helpful.
>
>-Thanks
>
>Rich Glazier
>
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