Subject: Re: Slow restoration question
From: Scott Marlowe <smarlowe@g2switchworks.com>
To: Michael Stone <mstone+postgres@mathom.us>
Cc: pgsql-performance@postgresql.org
In-Reply-To: <20060503205306.GB16533@mathom.us>
References: <20060502215329.GI97354@pervasive.com>
	<4A7F9950-65E0-4FA5-9FEC-BA1A93E615E5@clickspace.com>
	<20060503121847.GN31328@mathom.us>
	<30D5959B-3CCD-4CB4-B2D7-30DEA9F08BB6@torgo.978.org>
	<20060503155938.GO31328@mathom.us>
	<1146672434.22037.38.camel@state.g2switchworks.com>
	<20060503170604.GP31328@mathom.us>
	<20060503180821.GZ97354@pervasive.com>
	<20060503192652.GA16533@mathom.us>
	<1146685215.22037.46.camel@state.g2switchworks.com>
	<20060503205306.GB16533@mathom.us>
Content-Type: text/plain
Content-Transfer-Encoding: 7bit
Message-Id: <1146691831.22037.50.camel@state.g2switchworks.com>
Mime-Version: 1.0
Date: Wed, 03 May 2006 16:30:32 -0500

On Wed, 2006-05-03 at 15:53, Michael Stone wrote:
> On Wed, May 03, 2006 at 02:40:15PM -0500, Scott Marlowe wrote:
> >Note that I'm referring to bonnie++ as was an earlier poster.  It
> >certainly seems capable of giving you a good idea of how your hardware
> >will behave under load.
> 
> IME it give fairly useless results. YMMV. Definately the numbers posted 
> before seem bogus. If you have some way to make those figures useful in 
> your circumstance, great. Too often I see people taking bonnie numbers 
> at face value and then being surprised that don't relate at all to 
> real-world performance. If your experience differs, fine.

I think the real problem is that people use the older bonnie that can
only work with smaller datasets on a machine with all the memory
enabled.  This will, for certain, give meaningless numbers.

OTOH, having used bonnie++ on a machine artificially limited to 256 to
512 meg or ram or so, has given me some very useful numbers, especially
if you set the data set size to be several gigabytes.

Keep in mind, the numbers listed before likely WERE generated on a
machine with plenty of memory using the older bonnie, so those numbers
should be bogus.

If you've not tried bonnie++ on a limited memory machine, you really
should.  It's a quite useful tool for a simple first pass to figure out
which RAID and fs configurations should be tested more thoroughly.