JBOD versus RAID
Very often I get questions regarding the use of JBOD (Just a Bunch of Disks) in Exchange 2010.
In earlier versions of Exchange a RAID solution for storage was always recommended. RAID-10 offers the best performance and should always be used for large Exchange 2003 deployments. Exchange 2007 was well capable of working with RAID-5 solutions. RAID-5 offers less performance than RAID-10, but Exchange 2007 is less demanding.
Remeber that RAID is being used by Exchange for redundancy. If a disk fails, the only thing that needs to be done is rebuild the particular drive. And it's fully automatic, you only have to replace the disk.
JBOS is just the usage of a disk, whether it be a SAS or a SATA disk, it's just a simple, single disk and therefore offers no redundancy at all.
If you have only one Exchange 2010 Mailbox server with no redundancy on Mailbox Database level, you should always use a RAID solution for storage.
If you have two Exchange 2010 Mailbox Servers in a Database Availability Group (DAG) you should still use a RAID solution on both Mailbox Servers.
Only if you have three Exchange 2010 Mailbox Servers in a DAG, Microsoft recommends to use a JBOS solution.
Should you use SATA or SAS disks in a JBOD? SATA is well possible, but SAS still has better numbers when it comes to I/O, but also when it comes to reliability. My personal preference is SAS (even 1TB, 7200 RPM SAS disks), but I've been doing successfull tests with SATA as well.