On 9/9/2010 2:15 AM, taemun wrote:
Erik: does that mean that keeping the number of data drives in a raidz(n) to a power of two is better? In the example you gave, you mentioned 14kb being written to each drive. That doesn't sound very efficient to me.
(when I say the above, I mean a five disk raidz or a ten disk raidz2, etc)

Cheers,

Well, since the size of a slab can vary (from 512 bytes to 128k), it's 
hard to say. Length (size) of the slab is likely the better 
determination. Remember each block on a hard drive is 512 bytes (for 
now).  So, it's really not any more efficient to write 16k than 14k (or 
vice versa). Both are integer multiples of 512 bytes.
IIRC, there was something about using a power-of-two number of data 
drives in a RAIDZ, but I can't remember what that was. It may just be a 
phantom memory.

--
Erik Trimble
Java System Support
Mailstop:  usca22-123
Phone:  x17195
Santa Clara, CA
Timezone: US/Pacific (GMT-0800)

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