Re: Very poor read performance, query independent

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Charles Nadeau <charles(dot)nadeau(at)gmail(dot)com>
Cc: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Very poor read performance, query independent
Date: 2017-07-10 19:24:04
Message-ID: CAMkU=1z92pimpoDV1oTpd4AvSHS0CrLzQDFSxw1Z5cpmmjEOkw@mail.gmail.com
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On Mon, Jul 10, 2017 at 7:03 AM, Charles Nadeau <charles(dot)nadeau(at)gmail(dot)com>
wrote:

>
> 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.
>

That doesn't seem right. Sequential is only 43% faster? What job file are
giving to fio?

What do you get if you do something simpler, like:

time cat ~/$PGDATA/base/16402/*|wc -c

replacing 16402 with whatever your biggest database is.

Cheers,

Jeff

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