March 13, 2009 at 8:55 am
Have two options here. Currently have all tempdb data files locally on a RAID 1.
Have the option to put them on a iSCSI attached RAID 50.
Is having them locally better?
Should they be on the SAN?
Anyone have an opinion?
MCITP, Database Administrator
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March 13, 2009 at 9:07 am
no better, in general. I hate to say it, but "it depends"
Do you get better performance on the local v remote? Maybe a SQL IOSIM to test some throughput and then decide what makes sense. I like local over the network since it seems more stable. dedicated HBA to the SAN isn't the same as a network. Technically it's similar, but if you share traffic for other stuff with iSCSI then I get worried.
If it's dedicated network links to the iSCSI, or not a lot of bursty traffic, I might use that.
March 13, 2009 at 9:27 am
yea, the thing is that there's a ton of traffic on that iSCSI and that's why I'm leaning towards leaving them local.
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March 13, 2009 at 12:44 pm
I would look at the SAN/HBA option if it's available. If it is relatively modern, configured and aligned correctly, and running lots of write cache, you should see improvements proportional to gains in throughput.
I have been a big fan of iSCSI lately, but if you have a tempdb that is getting hammered, that could ruin an iSCSI node for all of the hosts conencted to it, and possibly degrade your SQL performance too.
Ed
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March 13, 2009 at 1:39 pm
I think it's been mentioned here that multiple data files for tempdb will improve performance, even if those multiple files are all in the same location. I don't recall why, though.
March 13, 2009 at 7:26 pm
yea, multiple tempdb data files can help with contention.
Usually you start with the # of files = to the cpu count.
I've got that part, and there all in the same place locally on that RAID 1.
I'm thinking like Steve that they may do best there for now. Moving a big MDF tomorrow that should help some of the I/O stuff going on.
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