Message-ID: <4679A822.9030104@g2switchworks.com>
Date: Wed, 20 Jun 2007 17:20:18 -0500
From: Scott Marlowe <smarlowe@g2switchworks.com>
User-Agent: Thunderbird 1.5.0.4 (X11/20060516)
MIME-Version: 1.0
To: christian.braun@tudor.lu
CC: pgsql-performance@postgresql.org
Subject: Re: Hardware suggestions
References: 
 <OF414BF8DA.327C4584-ONC12572FF.00398A72-C12572FF.00398A77@tudor.lu>
In-Reply-To: 
 <OF414BF8DA.327C4584-ONC12572FF.00398A72-C12572FF.00398A77@tudor.lu>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 8bit

christian.braun@tudor.lu wrote:
> Hi list members,
>
> I have a question regarding hardware issues for a SDI (Spatial data 
> infrastructure). It will consist of PostgreSQL with PostGIS and a UMN 
> Mapserver/pmapper set up.
> At our institute we are currently establishing a small GIS working 
> group. The data storage for vector data should be the central PostGIS 
> system. Raster data will be held in file system.
> Mostly the users are accessing the data base in read only mode. From 
> the client side there is not much write access this only will be done 
> by the admin of the system to load new datasets. A prototype is 
> currently running on an old desktop pc with ubuntu dapper - not very 
> powerfull, of course!
> We have about 10000 € to spend for a new server including the storage. 
> Do you have any recommendations for us?
> I have read a lot of introductions to tune up PostgreSQL systems. 
> Since I don't have the possibility to tune up the soft parameters like 
> cache, mem sizes etc., I wondered about the hardware. Most things were 
> about the I/O of harddisks, RAM and file system. Is the filesystem 
> that relevant? Because wo want to stay at Ubuntu because of the 
> software support, espacially for the GIS-Systems. I think we need at 
> least about 300-500Gb for storage and the server you get for this 
> price are about two dualcore 2.0 - 2.8 GHz Opterons.
> Do you have any suggestions for the hardware of a spatial data base in 
> that pricing category?

Pay as much attention to your disk subsystem as to your CPU / memory 
setup. Look at RAID-5 or RAID-10 depending on which is faster for your 
setup. While RAID-10 is faster for a system seeing plenty of updates, 
and a bit more resiliant to drive failure, RAID-5 can give you a lot of 
storage and very good read performance, so it works well for reporting / 
warehousing setups.

It might well be that a large RAID-10 with software RAID is a good 
choice for what you're doing, since it gets good read performance and is 
pretty cheap to implement. If you're going to be doing updates a lot, 
then look at a battery backed caching controller.

Memory is a big deal. As much as you can reasonably afford to throw at 
the system.

The file system can make a small to moderate impact on performance. Some 
loads are favored by JFS, others by XFS, and still others by ext2 for 
the data portion (only the pg_xlog needs to be on ext3 meta journaling only)