JBOD Vs Raid

We all know that Exchange 2010 can run on low cost Sata drives in a JBOD configuration as long you have at least 3 database copies. The reason is that because you have at least 3 copies on 3 different physical servers you can survive a single failed mailbox server. But is this a good Idea to relay on the integrity of a disk drive? But what if your hardware (e.g. disks) are from a faulty batch or contain buggy firmware and you equipped all three of your physical servers with those parts. I know of several occasions where a drive died in pairs within hours from each other.so recovering from this is unlikely.

I understand that, with DAGS, you can failover very quickly to a copy of the DB on another server. But with Raid protection (Raid5, Raid6 and Raid10) we can still lose a drive and still maintain data integrity. No failover at all needs to take place.  I understand that failovers are quick - but why even bothered failing over when you could use RAID. Below is form the WP “Exchange 2010-EMC-Storage best Practice” in this section the author talks about Raid protection and which one is best suitable for Exchange 2010

RAID 1/0 provides data protection by mirroring data onto another disk. This produces better performance and minimal or no performance impact in the event of disk failure. In general, RAID 1/0 is the best choice for Exchange Server 2010, especially if SATA and NL/SAS drives are used.

RAID 5 data is striped across disks in large stripe sizes. The parity information is stored across all disks so that data can be reconstructed. This can protect against a single-disk failure. For parity protection, RAID 5 generates one parity bit for every write. RAID 5 is most appropriate in environments with low IO requirements and where large mailboxes are being deployed. Data is striped across disks in large stripe sizes. The parity information is stored across all disks so that data can be reconstructed. This can protect against a single-disk failure. For parity protection, RAID 5 generates one parity bit for every write. RAID 5 is most appropriate in environments with low IO requirements and where large mailboxes are being deployed.

RAID 6 data is also striped across disks in large stripe sizes. However, two sets of parity information are stored across all disks so that data can be reconstructed, if required. RAID 6 can accommodate the simultaneous failure of two disks without data loss. RAID 6 generates two parity bits for every write.

My conclusion – the choice should be based on business requirements. Perhaps your business can do a few hours without e-mail while IT is recovering services. In that case it’s nice to have a supported low-cost JBOD/SATA option. In my opinion, the benefits of having proper RAID setup outweighs the trouble you have to go through when repairing your JBOD based solution.