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

From Scott Marlowe
Subject Re: [PERFORM] Very poor read performance, query independent
Date
Msg-id CAOR=d=0ut7s-PRrQX7thXjo8mSn1ssP4zhfjy6Y1TFm23KXKaA@mail.gmail.com
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In response to Re: [PERFORM] Very poor read performance, query independent  (Charles Nadeau <charles.nadeau@gmail.com>)
Responses Re: [PERFORM] Very poor read performance, query independent  (Charles Nadeau <charles.nadeau@gmail.com>)
List pgsql-performance
On Sat, Jul 15, 2017 at 11:53 AM, Charles Nadeau
<charles.nadeau@gmail.com> wrote:
> Mark,
>
> I increased the read ahead to 16384 and it doesn't improve performance. My
> RAID 0 use a stripe size of 256k, the maximum size supported by the
> controller.

Are your queries still spilling to disk for sorts? If this is the
case, and they're just too big to fit in memory, then you need to move
your temp space, where sorts happen, onto another disk array that
isn't your poor overworked raid-10 array. Contention between sorts and
reads can kill performance quick, esp on spinning rust.


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