On 2016-12-07 11:53, Martin Wilck wrote:
Rather than playing with tuning parameters, I'd suggest to proceed more systematically. Run some benchmarks to find out the "raw" performance of your disk for sequential and random IO. Do all this with the "noop" scheduler. I usually start out with a plain "dd" sequential read from the block device with 1M block size. If you have an unused partition, try sequential writes as well. Compare that to the device specs (or possibly with measurements you find on the net). This will give you an idea what to expect from the HW, and whether the HW is operating in the expected speed range.
You can measure the raw read speed with hdparm -Tt /dev/DEVICE -- Cheers / Saludos, Carlos E. R. (from 13.1 x86_64 "Bottle" at Telcontar)