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From: Jeff Janes <jeff.janes@gmail.com>
Date: Mon, 10 Jul 2017 12:24:04 -0700
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 <CAMkU=1z92pimpoDV1oTpd4AvSHS0CrLzQDFSxw1Z5cpmmjEOkw@mail.gmail.com>
Subject: Re: Very poor read performance, query independent
To: Charles Nadeau <charles.nadeau@gmail.com>
Cc: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
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On Mon, Jul 10, 2017 at 7:03 AM, Charles Nadeau <charles.nadeau@gmail.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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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On M=
on, Jul 10, 2017 at 7:03 AM, Charles Nadeau <span dir=3D"ltr">&lt;<a href=
=3D"mailto:charles.nadeau@gmail.com" target=3D"_blank">charles.nadeau@gmail=
.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"ma=
rgin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:=
1ex"><div dir=3D"ltr">
=09
=09
=09


<p style=3D"margin-bottom:0in;line-height:100%"><br></p>
<p style=3D"margin-bottom:0in;line-height:100%">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. </p></div></blockquote><div><br></div><div><br></div>=
<div>That doesn&#39;t seem right.=C2=A0 Sequential is only 43% faster?=C2=
=A0 What job file are giving to fio?</div><div><br></div><div>What do you g=
et if you do something simpler, like:=C2=A0</div><div><br></div><div>time c=
at ~/$PGDATA/base/16402/*|wc -c<br></div><div><br></div><div>replacing 1640=
2 with whatever your biggest database is.</div><div><br></div><div>Cheers,<=
/div><div><br></div><div>Jeff</div></div></div></div>

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