I want to know if it's better to hast DB server by SAS hard disk than SATA hard disk?
And it's also better to use RAID1.
I don't know much about RAID.
If the server is RAID6 default. Can I change it to RAID1? How?
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A bit more info on the hardware and what applications you are using (or planning to use) would help. – Dave M Feb 08 '12 at 15:38
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1You should read up on raid levels. RAID1 is probably not what you want. as an example. If you have a 8 disk raid 6 array of 500G disks, you would end up with (8-2)*500G = 3000G of usable storage. With RAID1, you'd get 500G of usable storage. – stew Feb 08 '12 at 15:55
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1You really should read our [Canonical RAID question](http://serverfault.com/questions/339128/what-are-the-different-widely-used-raid-levels-and-when-should-i-consider-them) - it has all your answers. – MikeyB Feb 08 '12 at 15:58
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I heard raid5 and raid6 are all slow. Better to do raid1+0 or raid0+1 to gain speed and safety. If disks are many, better raid1+0. Reasonable? – Hao Feb 09 '12 at 04:16
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"RAID5 and RAID6 are all slow." That's a vast oversimplification. Sometimes RAID5 is faster than RAID10, but for your case of a DB RAID10 is likely the best. And judging by your comment, you haven't read the Canonical RAID question which has LOTS of useful information in it. Please read. – MikeyB Feb 09 '12 at 14:49
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I want to know if it's better to hast DB server by SAS hard disk than SATA hard disk?
Depends. I am very happy witha system of 8 SATA discs (Velociraptor) and 2 SSD + operating system discs. Better is relative - also depends on needed speed. The window for SAS is narrow, though - need too much speed and SSD are cheaper. I use a SAS backplane, though. THe Server has now a total of 22 discs, 24 slots, the next upgrade puts it into a new case for 72 discs.
And it's also better to use RAID1.
Better than WHAT?
I don't know much about RAID.
Read the documentation.
If the server is RAID6 default. Can I change it to RAID1? How?
Depends on the server. Hardware raid? Did I mention it is a decent idea to read the documentation? Software - what OS?
In general, database servers either are trivial or require someone with knowledge what he does to plane the IO layout / budget properly.
