August 13, 2009 at 10:25 am
I've been having this discussion with a few people on Twitter but I wanted to bring it here so it may help some people. I also need it documented in one place so that I can convince those who make these decisions what is best.
I'm holding up the build on this server because I think it could be done better, but I'm running out of time on making a convincing argument.
The server is a PowerEdge R710. 5 SAS drives that are 146GB and 15k.
Normally they order 5 drives and set the first 2 up in a RAID 0 and make it the C: Drive for the OS. The other three drives would be made into a RAID 5 for everything else and called the D: Drive.
The first thing I've discovered is that the RAID 0 should be a RAID 1 in that current setup. It still may take some convincing even though that's black and white to me.
The biggest issue is what is the best setup for this server because they don't want to change the normal setup. Kendal Van Dyke offers some excellent info on the performance of different RAID levels here and that is helpful to an extent.
After talking with some folks on twitter I came away thinking that the best setup would be to put everything under a RAID 10. That means we'd have to steal a drive or take one away. We'd put the OS, AV software, and SQL Server Program files on that RAID however it was partitioned. It's difficult to use Kendal's info because it is related to the data side of things and if all of that is sitting on the SAN then it doesn't apply to the local server.
What I've got to show them is how RAID 10 would be better than RAID 5. Using Kendal's info I could possibly go there if we were going to have the system and user dbs on these drives but we won't.
Could you guys post your insight? Unfortunately I am on borrowed time and a decision may be made before I can make my case.
Update: Looks like it'll be 2 drives in RAID 1 and 3 drives in a RAID 5. Don't have enough to use to convince for RAID 10 instead of RAID 5 for just the program files.
MCITP, Database Administrator
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August 13, 2009 at 12:45 pm
I am not familiar with Dell servers. Probably your IT guys don't go with RAID 10 because the RAID card doesn't support RAID 10?
RAID 0 offers twice the space but no redundancy, if 1 drive fails you loose the whole RAID. Normally I put the OS, SQL log files on RAID 1 and SQL data files on RAID 5. This should be enough unless your server is being queried heavily. Also try to get 1 more drive for your RAID 5. 3 drives is minimum for RAID 5 but it is slow.
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