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Old 03-27-2007, 08:15 PM   #1
brentleary
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Best io-scheduler for Solid State Drive?


I am attempting to choose & tune an IO scheduler (CFQ, Deadline, Anticipatory, NoOp) for a Solid State Drive (SSD) instead of a rotating drive.

Based on recent characterizations of multiple SSD drives using iometer, their is a greater penalty for non-contiguous, random write accesses than with rotating media.

The loading scenario under which we are optimizing spawns 4 dd read & 3 dd write tasks running concurrently with RR scheduling. The dd task's block size is 300K.

Any advice as to which scheduler we could optimize to maximize sequential write access based on the above scenario would be greatly appreciated.

Thanks
 
Old 03-24-2009, 11:33 PM   #2
MACHINE
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NOOP scheduler is best used with solid state devices such as flash memory or in general with devices that do not depend on mechanical movement to access data (meaning typical "hard disk" drive technology consisting of seek time primarily, plus rotational latency). Such non-mechanical devices do not require re-ordering of multiple I/O requests, a technique that groups together I/O requests that are physically close together on the disk, thereby reducing average seek time and the variability of I/O service time.[2]

en.wikipedia.org/wiki/Noop_scheduler
 
Old 03-25-2009, 01:33 AM   #3
syg00
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Quote:
Originally Posted by brentleary View Post
Based on recent characterizations of multiple SSD drives using iometer, their is a greater penalty for non-contiguous, random write accesses than with rotating media.
Mmmm - that appears to depend on the quality of the equipment - and interpretation of the data.
Have a read of this - it's long but detailed.

NOOP would have to be a "no brainer" for the IO-scheduler - (I had thought it had a (tunable) delay for consolidating the I/Os, but a quick look at the code would seem not).
But I'd still reckon you'll get more benefit from spending a little more money for decent kit.
 
  


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