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Much difference in performance of 10GbE over 1Gb for iSCSI on DB cluster?

Posted on 2012-04-05
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Last Modified: 2012-05-16
I have a SQL Server 2008 cluster connected by iSCSI to my SAN. It connects via a 1Gb switch. The SAN I am using is an Equallogic PS4000, with a single RAID10 LUN. The disks are SAS 15k.  
Neither the switch nor the SAN have 10GbE capability, but I was considering an upgrade.
Would an upgrade to a 10GbE switch and SAN make much difference, or would I be constrained by Disk I/O regardless.
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Question by:sherryfitzgroup
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by:andyalder
ID: 37812410
Can't tell unless you run perfmon and see if physical disk: bytes/sec or Network interface bytes are flatlining due to lack of bandwidth. You'll have to look at both read and write.
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by:sherryfitzgroup
ID: 37896630
Thanks. Neither is flatlining as yet.
Theoretically though, if I upgraded my infrastructure to 10Gbs, what kind of disks would I need to match them in terms of I/O?
There would be no point in having the network infrastructure at this level if the performance was still hindered by the disks.
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andyalder earned 400 total points
ID: 37896831
If we assume the storage is set for 64K chunks and SQL is using 64k blocks all the time and that you would get 150 64K IOPS from a 15K disk then we can work it out. 150 * 64K = 9MB/s which is aprox 90 Mb/s, call it 100Mb/s per
mirrored pair of disks so 20 disks in RAID 10 = 1Gb/s, any more than that you would want 10Gb network. That's assuming the 1Gb is dedicated for server to storage and there's no storage to storage replication hitting the bandwidth.
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by:sherryfitzgroup
ID: 37974080
Thanks andy-good to know.
In the end I noticed that our 1Gb setup wasn't optimal. (multipathing was incorrectly configured)
This was fixed and resolved. Your calculations are useful though.
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