Messages in this thread | | | Date | Sun, 29 May 2005 21:03:00 +0200 | From | Jens Axboe <> | Subject | Re: Playing with SATA NCQ |
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On Sun, May 29 2005, Michael Thonke wrote: > Jens Axboe wrote, > > > > >There's really nothing to be tuned. If NCQ is enabled for your drive, it > >will be printed in dmesg after the lba48 flag, such as: > > > >ata1: dev 0 ATA, max UDMA/133, 488281250 sectors lba48 ncq > > > >If you don't see NCQ there, your drive/controller doesn't support it. > >Likewise you will have a queueing depth of > 1 if NCQ is enabled, check > >/sys/block/sdX/device/queue_depth to see what the configured queueing > >depth is for that device. > > > > > > > Hi Jens, > > thanks for the short info now my next question how many queue depths > are healty and wanted? > > For my Intel Corporation 82801GR/GH (ICH7 Family) Serial ATA Storage > Controllers cc=AHCI (rev 01) > and Samsung Hd160JJ SATAII drive the default queue is 30 > > ioGL64NX_MACH~# cat /sys/block/sda/device/{model,queue_depth} > SAMSUNG HD160JJ > 30 > > hdparm -Tt /dev/sda > > /dev/sda: > Timing cached reads: 4724 MB in 2.00 seconds = 2360.00 MB/sec > Timing buffered disk reads: 164 MB in 3.02 seconds = 54.28 MB/sec > > On random access the drives is a bit noisy but the subjective feeling > is great everything goes a bit faster.
You should see a nice performance improvement on random reads mainly, with streamed threaded reads being a bit faster as well. Write performance will be the same, if you had write back caching on before. So the real win is random reads, and that can be a pretty big win.
Actually I would say that the drive should sound _less_ noisy if NCQ is being really effective. Hard to judge of course, very subjective :)
> And whats about the option /sys/block/sdx/device/queue_type = simple > what can be done here?
Nothing, unfortunately NCQ doesn't provided any way of doing ordered tags. The only tunable is the queue_depth, you can set that anywhere between 1 and 30.
-- Jens Axboe
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