From: Scott Marlowe <scott.marlowe@gmail.com>
To: Rafael Domiciano <rafael.domiciano@gmail.com>
Cc: Matthew T. O'Connor <matthew@zeut.net>
Cc: Rafael Martinez <r.m.guerrero@usit.uio.no>
Cc: pgsql-admin@postgresql.org <pgsql-admin@postgresql.org>
Subject: Re: Vacuum Problems
Date: Mon, 8 Dec 2008 10:28:16 -0700
Message-ID: <dcc563d10812080928s90e324ch2978ffdd4e586225@mail.gmail.com> (raw)
In-Reply-To: <3a0028490812080917n170df296kfe33a2733a0d0377@mail.gmail.com>
References: <3a0028490811260543x74d02719w775a457999cfc74@mail.gmail.com>
<492DA95D.3010303@zeut.net>
<dcc563d10811261304g617b9806yf1208c4d5279ebee@mail.gmail.com>
<3a0028490812080504x22618c6fxd7df8febaadb1632@mail.gmail.com>
<dcc563d10812080735h42d94633v46449d9933dd22c@mail.gmail.com>
<3a0028490812080811r1c8a4756i1a1a514911741def@mail.gmail.com>
<dcc563d10812080817g5cc14e4bt1b573eb7edfb7e5e@mail.gmail.com>
<3a0028490812080829t1f485ec3g66626e8c4e2b610c@mail.gmail.com>
<dcc563d10812080835o593d7a76pe564cfceb86f867c@mail.gmail.com>
<3a0028490812080917n170df296kfe33a2733a0d0377@mail.gmail.com>
On Mon, Dec 8, 2008 at 10:17 AM, Rafael Domiciano
<rafael.domiciano@gmail.com> wrote:
> Here's the output. While the process was running my database get sometime
> without doing anything.
> You said that I probably get low numbers, but what numbers?
We're looking for MB/s and the bi/bo fields in bmstat (blocks in / blocks out)
> [root@postgres banco]# time dd if=/dev/zero of=/banco/testfile bs=1000000
> count=500
> 500+0 records in
> 500+0 records out
> 500000000 bytes (500 MB) copied, 85,4485 seconds, 5,9 MB/s
> real 1m25.451s
> user 0m0.003s
> sys 0m1.617s
> [root@postgres banco]# time dd of=/dev/null if=/banco/testfile
> 976562+1 records in
> 976562+1 records out
> 500000000 bytes (500 MB) copied, 47,5025 seconds, 10,5 MB/s
> real 0m47.543s
> user 0m0.457s
> sys 0m1.470s
> And the vmstat output:
>
> procs -----------memory---------- ---swap-- -----io---- --system--
> -----cpu------
> r b swpd free buff cache si so bi bo in cs us sy id
> wa st
> 0 8 111760 56432 19812 1305692 0 0 744 832 2488 1518 5 3 46
> 46 0
Here, the bi/bo numbers are 768 in and 832 out. That's k/second we're
looking at.
Lots of the same numbers cut out.
> procs -----------memory---------- ---swap-- -----io---- --system--
> -----cpu------
> r b swpd free buff cache si so bi bo in cs us sy id
> wa st
> 0 6 111760 55452 18528 1296412 0 0 88 25040 1843 1436 2 3 34
> 61 0
> 1 7 111760 52352 18540 1296472 0 0 36 15220 1467 944 3 2 27
> 68 0
> 0 6 111760 54152 18552 1296568 0 0 88 42296 1609 822 1 2 38
> 59 0
> 1 8 111760 52412 18580 1296752 0 0 172 27052 1567 950 2 3 27
> 69 0
> 0 6 111724 53904 18632 1297008 320 0 580 1504 1902 2320 5 6 23
> 66 0
> 1 6 111724 54280 18660 1297200 4 0 200 1060 2014 1783 5 3 44
> 48 0
> 1 7 111676 51388 16340 1302348 8 0 156 1212 1684 848 2 2 53
> 42 0
> 1 6 111668 55040 14864 1301048 0 4 152 46328 1595 5108 1 5 40
> 54 0
Now we're showing that we can write to the disk at 25 to 42 Megs a
second, not too bad. But it looks really bursty, like it can sustain
this throughput for only a few seconds. Try writing a larger file
and run vmstat 10 or 60 as well and see what the average over a longer
time with a larger file is. I get a feeling your machine has a hard
time sustaining throughput for some reason.
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To: pgsql-admin@postgresql.org
Cc: scott.marlowe@gmail.com, rafael.domiciano@gmail.com, matthew@zeut.net, r.m.guerrero@usit.uio.no
Subject: Re: Vacuum Problems
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