Message-ID: <50C0577A.6070401@kickstone.com>
Date: Thu, 06 Dec 2012 08:29:46 +0000
From: John Lister <john.lister@kickstone.com>
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To: Andrea Suisani <sickpig@opinioni.net>,
 pgsql-performance@postgresql.org
Subject: Re: xfs perform a lot better than ext4 [WAS: Re: Two identical
	systems, radically different performance]
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> on this box:
>
>> in a brief: the box is dell a PowerEdge r720 with 16GB of RAM,
>> the cpu is a Xeon 5620 with 6 core, the OS is installed on a raid
>> (sata disk 7.2k rpm) and the PGDATA is on separate RAID 1 array
>> (sas 15K rpm) and the controller is a PERC H710 (bbwc with a cache
>> of 512 MB). (ubuntu 12.04)
>
> on the same machine with the same configuration,
> having PGDATA on a xfs formatted partition gives me
> a much better TPS.
>
> e.g. pgbench  -c 20 -t 5000 gives me 6305 TPS
> (3 runs with "echo 3 > /proc/sys/vm/drop_caches && 
> /etc/init.d/postgresql-9.2 restart"
> in between).
Hi, I found this interesting as I'm trying to do some benchmarks on my 
box which is very similar to the above but I don't believe the tps is 
any where near what it should be. Is the 6305 figure from xfs? I'm 
assuming that your main data array is just 2 15k sas drives, are you 
putting the WAL on the data array or is that stored somewhere else? Can 
I ask what scaling params, etc you used to build the pgbench tables and 
look at your postgresql.conf file to see if I missed something (offline 
if you wish)

I'm running 8x SSDs in RAID 10 for the data and pull just under 10k on a 
xfs system which is much lower than I'd expect for that setup and isn't 
significantly greater than your reported results, so something must be 
very wrong.

Thanks

John


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