On 2016-09-23 15:38, Greg Troxel wrote:
Johnny Billquist <bqt%softjar.se@localhost> writes:With rotating rust, the order of operations can make a huge difference in speed. With SSDs you don't have those seek times to begin with, so I would expect the gains to be marginal.For reordering, I agree with you, but the SSD speeds are so high that pipeling is probably necessary to keep the SSD from stalling due to not having enough data to write. So this could help move from 300 MB/s (that I am seeing) to 550 MB/s.
Good point. In which case (if I read you right), it's not the reordering that matters, but the simple case of being able to queue up several operations, to keep the disk busy. And potentially running several disks in parallel. Keeping them all busy. And we of course also have the pre-processing work before the command is queued, which can be done while the controller is busy. There are many potential gains here.
Johnny
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