Re: Postgres on RAID5

>On Fri, 11 Mar 2005 16:13:05 -0500, Arshavir Grigorian <ag@m-cam.com> wrote:
>
>
>>Hi,
>>
>>I have a RAID5 array (mdadm) with 14 disks + 1 spare. This partition has
>>an Ext3 filesystem which is used by Postgres. Currently we are loading a
>>50G database on this server from a Postgres dump (copy, not insert) and
>>are experiencing very slow write performance (35 records per second).
>>
>>

That isn't that surprising. RAID 5 has never been known for its write
performance. You should be running RAID 10.

Sincerely,

Joshua D. Drake


>>Top shows that the Postgres process (postmaster) is being constantly put
>>into D state for extended periods of time (2-3 seconds) which I assume
>>is because it's waiting for disk io. I have just started gathering
>>system statistics and here is what sar -b shows: (this is while the db
>>is being loaded - pg_restore)
>>
>>               tps        rtps     wtps      bread/s  bwrtn/s
>>01:35:01 PM    275.77     76.12    199.66    709.59   2315.23
>>01:45:01 PM    287.25     75.56    211.69    706.52   2413.06
>>01:55:01 PM    281.73     76.35    205.37    711.84   2389.86
>>
>>
>>
>[snip]
>
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