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Re: WALL on controller without battery?

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: WALL on controller without battery?
Date: 2007-07-11 23:01:10
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Wed, 11 Jul 2007, Francisco Reyes wrote:

> I am re-working the specs of the machine to try and get a 4port 3ware to have 
> the battery backup.

That's really not necessary, it just would be better (and obviously more 
expensive).  The warnings you've been getting here have been to let you 
know that you absolutely can't put the WAL on the controller with the OS 
disks attached without making compromises you probably won't be happy 

> During peak operation there will be about 5 to 20 updates per second 
> with a handfull of reads.

There really is no reason you need to be concerned about WAL from a 
performance perspective if this is your expected workload.  If you're 
working with a tight budget, the original design you had was perfectly 
fine.  Just use all the disks on the big controller as a large volume, put 
both the database and the WAL on there, and don't even bother trying to 
separate out the WAL.  If you expected hundreds of updates per second, 
that's where you need to start thinking about a separate WAL disk, and 
even then with 8 disks to spread the load out and a good caching 
controller you might still be fine.

* Greg Smith gsmith(at)gregsmith(dot)com Baltimore, MD

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