Re: Amazon High I/O instances

[Sébastien Lorion <sl@xxxxxxxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxx> 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.

--
john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast




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