On Mon, Jul 10, 2017 at 9:03 AM, Charles Nadeau <charles.nadeau@xxxxxxxxx> wrote: > I’m running PostgreSQL 9.6.3 on Ubuntu 16.10 (kernel 4.4.0-85-generic). > Hardware is: > > *2x Intel Xeon E5550 > > *72GB RAM > > *Hardware RAID10 (4 x 146GB SAS 10k) P410i controller with 1GB FBWC (80% > read/20% write) for Postgresql data only: > > The problem I have is very poor read. When I benchmark my array with fio I > get random reads of about 200MB/s and 1100IOPS and sequential reads of about > 286MB/s and 21000IPS. But when I watch my queries using pg_activity, I get > at best 4MB/s. Also using dstat I can see that iowait time is at about 25%. > This problem is not query-dependent. Stop right there. 1100 iops * 8kb = ~8mb/sec raw which might reasonably translate to 4mb/sec to the client. 200mb/sec random read/sec on spinning media is simply not plausible; your benchmark is lying to you. Random reads on spinning media are absolutely going to be storage bound. merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
