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8.2 slower than 8.1?

From: Brian Ghidinelli <brian(at)pukkasoft(dot)com>
To: SF Postgres <sfpug(at)postgresql(dot)org>
Subject: 8.2 slower than 8.1?
Date: 2007-12-28 01:43:16
Message-ID: (view raw, whole thread or download thread mbox)
Lists: sfpug
About 2 years ago, I ran some benchmarks on a Compaq DL380G2 I use for 
Postgres[1].  I tested a variety of disk configurations to compare 
setups.  I'm rebuilding the machine now with upgraded hardware and I'm 
dumbfounded by substantially slower performance.  Here are the specs:

Compaq DL380G2, 2x1.44ghz, six internal disks with Smart Array 5i 

			Prior			Now
OS			CentOS 4.2		CentOS 5.0
Filesystem		ext3			ext3
postgresql.conf		Stock			Stock
Ram			1 GB			3 GB
Postgres		8.1.2			8.2.5
Smart Array		5i (builtin, 16mb)	5302 (128mb cache)
Drive Config		2 disk RAID-1 (os/log)	2 disk RAID-1 (os)
			4 disk RAID-10 (data)	4 disk RAID-10 (log)
						14 disks RAID-10 (data)

I'm using the six internal disks as a 2-disk raid-1 mirror for the OS 
and 4-disk raid-10 for the log on the internal 5i controller.  I have an 
external 14-disk raid-10 connected to a Smart Array 5302 (with 128gb 
cache in a 75%/25% read/write setup).

I ran my benchmark script again (see below) and the performance dropped 
60% at 1 and 2 users and 27% and 17% at 5 and 10 users respectively.

Any ideas what might lead to this decrease across the board?



Here is my simple script:

for c in 1 2 5 10
         echo "Starting test for $c users..." 1>&2
         echo "== $c concurrent users, 500 transactions =============="
         dropdb testdb -U $USER
         createdb testdb -U $USER
         echo "Initializing benchmark database"
         pgbench -i -U $USER -s 10 testdb &> /dev/null
         echo "===== sync ======"
         sync;sync;sync;sleep 10
         pgbench -n -U $USER -t 500 -h $HOST -c $c $DB 2>&1


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Next:From: Josh BerkusDate: 2008-01-03 21:55:43
Subject: Re: 8.2 slower than 8.1?
Previous:From: R.P. AdityaDate: 2007-12-13 03:17:13
Subject: Re: Can Oracle do what PostgreSQL can?

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