Justin Piszcz wrote:
Without NCQ, performance is MUCH better on almost every operation, with
the exception of 2-3 items.
Variables to take into account:
* the drive (NCQ performance wildly varies)
* the IO scheduler
* the filesystem (if not measuring direct to blkdev)
* application workload (or in your case, benchmark tool)
* in particular, the threaded-ness of the apps
For the overwhelming majority of combinations, NCQ should not /hurt/
performance.
For the majority of combinations, NCQ helps (though it may not be often
that you use more than 4-8 tags).
In some cases, NCQ firmware may be broken. There is a Maxtor firmware
id, and some Hitachi ids that people are leaning towards recommending be
added to the libata 'horkage' list.
Jeff
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