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Re: [PERFORM] Very poor read performance, query independent - Mailing list pgsql-performance

From bricklen
Subject Re: [PERFORM] Very poor read performance, query independent
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Msg-id CAGrpgQ89GO51Esvg=AE7-k=ypxrQSE_trzG5pAL16N2JhiX+vA@mail.gmail.com
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In response to Re: [PERFORM] Very poor read performance, query independent  (Charles Nadeau <charles.nadeau@gmail.com>)
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On Wed, Jul 12, 2017 at 12:30 AM, Charles Nadeau <charles.nadeau@gmail.com> 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.

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