Re: Playing with SATA NCQ

Jens Axboe
2005-05-30T06:13:19Z

On Sun, May 29 2005, Michael Thonke wrote:
> >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.
> >
> >
> >
> So way my drive got default 30 as queue_depth on AHCI as you mentoined
> in the next mail
> 2-4 should be suitable and enough/normal?

Yes, 30 will be default for basically anyone as ahci now advertises a
max depth of 30 and the drives typically all support a depth of 32. The
minimum value of those two is used.

Whether 2-4 is 'enough' depends on your workload. But usually 2-4 is
enough to get a nice speedup on heavier io, while still getting you good
latencies on the individual io.

--
Jens Axboe