dell 2T 7.2k nearline SAS 6Gbps- ingress/egress throughput

Solution 1:

A call to Dell should give you all of the information that you need. There are white papers and tech specs on all of this available if you call your rep.

Raid 10 is pretty much universally used where performance matters, but you should always test multiple scenarios. You could always be an edge case.

Solution 2:

Each 7.2k RPM drive can perform between 80-150 IO/s, assuming the workload is random small reads and writes. Writes will usually be cached by the raid controller, so will go as fast as the memory does until it's full. Raid 10 has a minimum of 4 drives, so your reads will be between 320 and 600 IO/s with the minimum number of drives.

If you choose raid 5, you will have more usable space, but your IO/s per drive on average might go down, depending on the raid controller you have and what percent of your workload is writes.

IO/s is a measure of performance that depends heavily on seek time, and an average seek time of about 6 ms is average for 7.2k RPM drives. You can get better by upgrading to 10 or 15k RPM, but you could also increase your effective read "speed" by increasing the number of 7.2k drives you stripe your data across.

Recommendations:

• Size your workload performance, and then fit your drives to meet or exceed it. If you think your web server is capable of doing 500 IO/s, go for 6 7.2k RPM drives.
• Choose your raid carefully- if you don't need space as much as you need speed, go with raid 10. It also allows you to lose as many as half your drives before having a loss of data. Raid 6 is also popular for large drives as it can lose two drives before failing, however introduces a heavy workload on your raid card.
• Invest in a decent battery backed cache raid card.