What is the best raid type for SQL Server in terms of performance and reliability?
Best Answer
Hands down if you needs lots of I/O you need to look at raid 10
RAID 1+0 (or 10) is a mirrored data set (RAID 1) which is then striped (RAID 0), hence the "1+0" name. A RAID 1+0 array requires a minimum of four drives: two mirrored drives to hold half of the striped data, plus another two mirrored for the other half of the data. In Linux MD RAID 10 is a non-nested RAID type like RAID 1, that only requires a minimum of two drives, and may give read performance on the level of RAID 0.
Also remember to put your TEMPDB on a separate disk for performance reasons. I'm sure Paul Randal will come in here and blow your mind with why in a bit.
We have a Poweredge 2950 running Hyper-V with a six disk RAID5 and there are no performance problems. This only runs ten VMs, so you could argue that it's not that heavily loaded, all the same the disk performance is very good. Very, very good in fact!
People seem to have a real downer on RAID5, and it's certainly true that if you have the array configured for write-through the write performance is poor. However the Perc 5/i and 6/i controllers seem to manage write caching very effectively and unless your system is doing an awful lot of writes I doubt disk speed would be a problem. Yes, RAID10 will be faster, but that isn't the same as saying that RAID5 is too slow.
Best Answer
Hands down if you needs lots of I/O you need to look at raid 10
RAID 1+0 (or 10) is a mirrored data set (RAID 1) which is then striped (RAID 0), hence the "1+0" name. A RAID 1+0 array requires a minimum of four drives: two mirrored drives to hold half of the striped data, plus another two mirrored for the other half of the data. In Linux MD RAID 10 is a non-nested RAID type like RAID 1, that only requires a minimum of two drives, and may give read performance on the level of RAID 0.