Re: Amazon High I/O instances

Disks are doing 150 read + 90 write ops/s when they should be able to do a
total of 1000 iops each as currently configured (this is the max that can
be set). Total bandwidth is 1000mb/s each too. So clearly, either there is
something wrong with ZFS/FreeBSD on Amazon (either because of config or
something deeper) or PostgreSQL is not fully utilizing the hardware, again
because of config or some other issue.

I will make another test instance with pg 9.2 this time.

Concerning shared_buffers and wal_buffers, I found this article interesting:

http://rhaas.blogspot.ca/2012/03/tuning-sharedbuffers-and-walbuffers.html

Sébastien

On Thu, Sep 13, 2012 at 5:28 PM, John R Pierce <pierce(at)hogranch(dot)com> wrote:

> On 09/13/12 2:08 PM, Sébastien Lorion wrote:
>
>> I started db creation over, this time with 16GB maintenance_work_mem and
>> fsync=off and it does not seem to have a great effect. After again 5 hours,
>> during index creation, disk and cpu are barely used: 95% idle and 2-3 MB/s
>> writes (150 reads/s, 90 writes/s).
>>
>
> I've never had to set maintenance_work_mem any higher than 1gb for plenty
> good enough performance.
>
> whats the %busy on the disk ? if you have a slow disk device (such as a
> shared virtual disk), 90 write/sec may be all its good for. MB/s is fairly
> meaningless when dealing with random committed writes.
>
>
>
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>
>
> --
> john r pierce N 37, W 122
> santa cruz ca mid-left coast
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