Sql-server – Installation of SQL Server RAID 10 vs RAID 5

Conventional wisdom about RAID doesn't apply well to SSDs. They don't really need striping (RAID0). They are prone to failures by-design, but RAID-1 is usually not the right answer for SSD for two reasons: a) is wasteful, halves the capacity of the SSD array (and they are pricey) and 2) SSDs failure characteristics leads towards both drives in the mirror to fail at very close intervals (ie. correlated failures) and thus render the entire array useless. See Differential RAID: Rethinking RAID for SSD Reliability for a lengthier discussion. Some have recommended using Raid-6 for SSDs.

Additionally, the conventional wisdom of SQL Server file layout doesn't apply to SSDs. I would recommend you watch SQL on SSDs: Hot and Crazy Love and go over the benchmark links in this answer.

1. I would only use RAID 0 for the logs if you're okay with having reduced disaster recovery capability. You won't be able to make log tail backups in the event of a disk failure, and will only be able to restore to your most recent backup. However, this may be less of an issue if you're running Availability Groups, particularly with synchronous mirroring. You generally won't have any performance overhead for RAID 1 vs. a single non-RAID disk, but you will have better I/O performance with RAID 0 instead of RAID 1 for an equal number of disks.

2. Be aware that tempdb also has both data files and log files, and those could end up interfering with each other (performance wise) if placed on the same volume. You may want to consider foregoing the spare disk and using it for tempdb logs instead if performance still isn't acceptable. If your C: array is large enough, you might be able to get away with using it for on-disk backups, though you should probably partition it to prevent runaway backups from filling your OS disk.