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From: Fernando Hevia <fhevia@ip-tel.com.ar>
To: pgsql-performance@postgresql.org
Subject: new server I/O setup
Date: Thu, 14 Jan 2010 17:03:52 -0300
Message-ID: <3CD96C0AB4114484BFE358A3EDE61C01@iptel.com.ar> (raw)

Hi all,
 
I've just received this new server:
1 x XEON 5520 Quad Core w/ HT
8 GB RAM 1066 MHz
16 x SATA II Seagate Barracuda 7200.12
3ware 9650SE w/ 256MB BBU
 
It will run an Ubuntu 8.04 LTS Postgres 8.4 dedicated server. Its database
will be getting between 100 and 1000 inserts per second (those are call
detail records of ~300 bytes each) of around 20 clients (voip gateways).
Other activity is mostly read-only and some non time-critical writes
generally at off peak hours.
 
So my first choice was:
 
2 discs in RAID 1 for OS + pg_xlog partitioned with ext2.
12 discs in RAID 10 for postgres data, sole partition with ext3.
2 spares
 
 
My second choice is:
 
4 discs in RAID 10 for OS + pg_xlog partitioned with ext2
10 discs in RAID 10 for postgres, ext3
2 spares.
 
The bbu caché will be enabled for both raid volumes.
 
I justified my first choice in that WAL writes are sequentially and OS
pretty much are too, so a RAID 1 probably would hold ground against a 12
disc RAID 10 with random writes.
 
I don't know in advance if I will manage to gather enough time to try out
both setups so I wanted to know what you guys think of these 2 alternatives.
Do you think a single RAID 1 will become a bottleneck? Feel free to suggest
a better setup I hadn't considered, it would be most welcome.
 
Pd: any clue if hdparm works to deactive the disks write cache even if they
are behind the 3ware controller?
 
Regards,
Fernando.
 

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