Messages in this thread | | | Date | Wed, 04 Jul 2007 10:19:55 +0900 | From | Tejun Heo <> | Subject | Re: Some NCQ numbers... |
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Hello,
Michael Tokarev wrote: > 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".
I see. Thanks for testing.
> 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?
No one would know without testing.
> 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)
Well, what the driver does is minimal. It just passes through all the commands to the harddrive. After all, NCQ/TCQ gives the harddrive more responsibility regarding request scheduling.
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