Messages in this thread | | | Date | Wed, 04 Jul 2007 00:29:27 +0400 | From | Michael Tokarev <> | Subject | Re: Some NCQ numbers... |
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Tejun Heo wrote: > Michael Tokarev wrote: [] >> A test drive is Seagate Barracuda ST3250620AS "desktop" drive, >> 250Gb, cache size is 16Mb, 7200RPM. [test shows that NCQ makes no difference whatsoever]
> And which elevator?
Well. It looks like the results does not depend on the elevator. Originally I tried with deadline, and just re-ran the test with noop (hence the long delay with the answer) - changing linux elevator changes almost nothing in the results - modulo some random "fluctuations".
In any case, NCQ - at least in this drive - just does not work. Linux with its I/O elevator may help to speed things up a bit, but the disk does nothing in this area. NCQ doesn't slow things down either - it just does not work.
The same's for ST3250620NS "enterprise" drives.
By the way, Seagate announced Barracuda ES 2 series (in range 500..1200Gb if memory serves) - maybe with those, NCQ will work better?
Or maybe it's libata which does not implement NCQ "properly"? (As I shown before, with almost all ol'good SCSI drives TCQ helps alot - up to 2x the difference and more - with multiple I/O threads)
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