Brandon High wrote:
On Fri, Mar 19, 2010 at 5:32 AM, Chris Dunbar - Earthside, LLC
<cdun...@earthside.net <mailto:cdun...@earthside.net>> wrote:
if I went with two? Finally, would I be better off with raidz2 or
something else instead of the striped mirrored sets? Performance
and fault tolerance are my highest priorities.
Performance and fault tolerance are somewhat conflicting.
You'll have good fault tolerance and performance using a wide raidz3
stripe, eg: 12-disk raidz3 with a spare.
Actually, except on certain loads (large, streaming write/read), this
config is going to give pretty poor performance.
You'll have the best fault tolerance using small raidz3 stripes with a
spare, for instance 2 x 6-disk raidz3. This uses 50% of your disks for
redundancy.
You'll have slightly better performance and slightly worse fault
tolerance using raidz2 instead in both cases above. I would not
recommend using raidz, as it will offer almost no real fault tolerance
with the size of drives you're using.
Realistically, a 2 x 6-disk raidz2 with a hot spare will provide
/almost/ the same level of redundancy as 2 x 6-disk raidz3, and about
30% better performance and space. (he said he had 13 disks)
You'll have your best performance and fault tolerance using 3-way
mirrors, but you sacrifice 2/3 of your disks to do it. Actually, I
think that raidz3 is higher tolerance still, but the performance
difference will be huge.
2-way mirrors is slightly worse for fault tolerance (below raidz2 I
believe) and good performance.
Yes - see my followup post for percentages of failures.
--
Erik Trimble
Java System Support
Mailstop: usca22-123
Phone: x17195
Santa Clara, CA
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