Comments on How To Build A Low Cost SAN
How To Build A Low Cost SAN In today's world there is a obvious need of information sharing in every department and network storage can help us to achieve this most growing challenge. Here in this article we are focusing our concentration to make a low-cost SAN.
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Comments
'ATA disks are not as reliable as their SCSI counterparts.'
This is wrong in this context. The reliability of hardware is not relevant for the protocol.
agree. In fact you can make a point that you can create a MORE reliable array for the same money out of SATA disks.
The reasoning here is that if you can buy a SATA disk for half the cost, you can simple buy your rundundant drives and have them on hand. The failure rate of SATA drives vs SAS drives is not double. Therefore you can get a more reliable array if you concede that you will replace drives at least slightly more often.
Additionally, you can have more levels of redundancy with SATA drives for the same money. Thinking of raid5 with a hot spare? how about raid6 with 2 hot spares? how about raid10 plus 2 hot spares? SATA drives are cheaper and larger so a raid10 can be had for less money than a SAS raid5.
drawbacks? RPMS. raptors defeat the advantage of SATA because of price. SAS drives are up to 15,000 RPMS. Luckily**, you are likely going to have a network bottleneck once you have 6 active disks (like a 12 disk raid10, you get the performance of 6 drives).
If you use a filesystem like XFS or ZFS you can use a very fast SSD to improve your i/o as XFS can push the transaction logs to a different device and ZFS can use a fast disk as an inline cache. This way you can get the benefits of SATA in drive size and price, and one fast/expensive SSD to help bridge the gap in access times (~8ms 7200rpm SATA, ~4ms 15krpm SAS)
" The failure rate of SATA drives vs SAS drives is not double. "
Desktop SATA - 10^14 URE rate
Enterprise SAS - 10^15 or better URE rate
What then?