March 1, 2011 at 9:45 am
I've only been doing this DBA thing for 4 months so please bare with me...
System admins are asking me to give them best practices for setting up LUNs for SQL Server in a clustered SAN environment. Using Fibre Channel.
The first thing I am being asked to address is the LUN configuration... Correct me if I am wrong here but this is what I am planning on doing. Also, I've read that the way SQL Server is configured on a FibreChannel SAN is pretty much out of my control and that I can pretty much only specify how much space I want. That the RAID and placement of backups to a seperate physical disk is not releavent. Either way here is what I'm looking at. Whether it happens or not is another story.
1. A LUN for data and/or log files (est to be 300GB) (How do I determine how many disks this should be made up of?
2. RAID 5 for the data files (.mdf)
3. RAID 0+1 for the transaction log files (should this be a seperate LUN? Can a LUN only have one type of RAID level or can a LUN be both RAID 0+1 and RAID 5?
4. A seperate LUN for Backups (say 200 GB)
5. RUN DiskPart.exe offset to align
6. Set the Allocation unit size to 64KB
7. Test using SQLIO
Thanks!
March 1, 2011 at 10:11 am
Use RAID 10 instead of 5. Faster writes (about 30% or so?). Requires at least one more disk.
Use RAID 10 instead of 0+1. Same disk numbers, but better fault tolerance (more physical drives can fail without the drive going down in some cases - depending on which drives fail).
Use a separate LUN for each drive set if possible.
Backup drive may need to be larger than the data drive to keep a tlog backups along with full backups.
Don't forget tempdb. This should be separated from the data drives to increase throughput. It would be nice if you could test, but you may find tempdb to be your IO bottleneck and you may actually want several tempdb data files on different drive sets. Prepare now for that if they are giving you what you are asking for!
Jim
Jim Murphy
http://www.sqlwatchmen.com
@SQLMurph
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