IO Speeds with 4x SATA vs 2x SATA + 2x SAS for MySQL

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Posted by Squidix - SamBarrow, 02-16-2011, 11:42 PM
What would be better in your opinion for IO speeds? This is a shared hosting server with cpanel, about as generic as it gets. 4x SATA 7.2K in RAID 10 2x SATA 7.2K in RAID 1 + 2x SAS 15K in RAID 1 (for MySQL only)
Posted by Patrick, 02-17-2011, 12:25 AM
I'd personally opt for the RAID10, although I know some people will disagree. My reason is that you'll find things slow down pretty bad with RAID1 when you're putting hundreds of clients on that server and then someone decides to do a large cPanel backup during the middle of the day. You need to consider the overall IO performance and while 2x SAS 15K hard drives would be nice for MySQL, that's only one aspect of the server operations... The OS, Apache, PHP, etc, will still run off the RAID1 array which will be much slower than a RAID10 array.
Posted by DJMizt73, 02-17-2011, 02:33 AM
you need to consider your controller speed also. Almost all onboard raid controllers are faker raids (soft raid) and they really do not take advantage of the higher IO speeds of SAS drives. If thats your case you may not see any major difference in your proposed setups. Having said that, if your app is going to be mysql heavy then I would split it (like your 2nd option). At least here you are dedicating IO just for mysql. If its going to be a vanilla shared host - then a RAID10 makes more sense.
Posted by mellow-h, 02-17-2011, 02:53 AM
You would probably need to figure this out analyzing some data from your current server statistics. If your mysql is causing the bottleneck of your IO, only then you should consider the second configuration, otherwise, a balanced configuration like the first one would probably the best.

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