On Sun, 13 Feb 2011, Dave Crooke wrote:
For any database, anywhere, the answer is pretty much always RAID-10.
The only time you would do anything else is for odd special cases.
there are two situations where you would opt for something other than
RAID-10
1. if you need the space that raid 6 gives you compared to raid 10 you may
not have much choice
2. if you do almost no updates to the disk during the time you are doing
the reads then raid 6 can be at least as fast as raid 10 in non-degraded
mode (it could be faster if you are able to use faster parts of the disks
in raid 6 than you could in raid 10). degraded mode suffers more, but you
can tolerate any 2 drives failing rather than just any 1 drive failing for
raid 10 (the wrong two drives failing can kill a raid 10, while if the
right drives fail you can loose a lot more drives in raid 10)
where raid 6 is significantly slower than raid 10 is when you are doing
small random writes. Also many the performance variation between raid
controllers will be much higher with raid 6 than with raid 10
David Lang
Cheers
Dave
On Sun, Feb 13, 2011 at 2:12 PM, sergey <sergey.on.net@xxxxxxxxx> wrote:
Hello,
I got a disk array appliance of 8 disks 1T each (UltraStor RS8IP4). It will
be used solely by PostgresQL database and I am trying to choose the best
RAID level for it.
The most priority is for read performance since we operate large data sets
(tables, indexes) and we do lots of searches/scans, joins and nested
queries. With the old disks that we have now the most slowdowns happen on
SELECTs.
Fault tolerance is less important, it can be 1 or 2 disks.
Space is the least important factor. Even 1T will be enough.
Which RAID level would you recommend in this situation. The current options
are 60, 50 and 10, but probably other options can be even better.
Thank you!
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