Re: Very poor read performance, query independent

[bricklen <bricklen@xxxxxxxxx>]

On Wed, Jul 12, 2017 at 12:30 AM, Charles Nadeau <charles.nadeau@xxxxxxxxx> wrote:

I use noop as the scheduler because it is better to let the RAID controller re-arrange the IO operation before they reach the disk. Read ahead is set to 128:

charles@hpdl380g6:~$ cat /sys/block/sdc/queue/read_ahead_kb

128

charles@hpdl380g6:~$ cat /sys/block/sdc/queue/scheduler

[noop] deadline cfq 

Perhaps pg_test_fsync (https://www.postgresql.org/docs/9.6/static/pgtestfsync.html) and pg_test_timing will help shed some light here, or at the very least give some numbers to compare against.