MD RAID - disable NCQ

Solution 1:

Thanks for your answer.

Wikipedia states "NCQ can negatively interfere with the operating system's I/O scheduler, actually decreasing performance" and it refers to this article http://www.cs.albany.edu/~sdc/CSI500/Fal10/DiskArmSchedulingPapers/a2-yu.pdf

This article states "Under a random workload, the I/O scheduler should be disabled, that is, noop, and NCQ in charge of scheduling requests entirely; when under a sequential workload, an I/O scheduler should take full charge of scheduling them instead of NCQ. It implies that the type of information that can help scheduling decision can vary according to the workload type."

Thus it seems to be a problem under a sequential workload, but not under a random workload.

At conclusions it states that "In the long run, we suggest that a new SATA 2 specification should contain a well-defined interface to fully control NCQ mechanism."

But this article is rather old (March 2010) and I don't know if it has been solved.