Message-ID: <50C06652.2080902@opinioni.net>
Date: Thu, 06 Dec 2012 10:33:06 +0100
From: Andrea Suisani <sickpig@opinioni.net>
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To: John Lister <john.lister@kickstone.com>
CC: 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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[added performance list back]

On 12/06/2012 10:04 AM, John Lister wrote:
> Thanks for the info, I'll have a play and see what values I get with similar settings, etc

you're welcome

> Still think something is wrong with my config, but we'll see.

which kind of ssd disks do you have ?
maybe they are of the same typeShaun Thomas is having problem with here:
http://archives.postgresql.org/pgsql-performance/2012-12/msg00030.php

Andrea


> john
>
> On 06/12/2012 08:44, Andrea Suisani wrote:
>> Hi John,
>>
>> On 12/06/2012 09:29 AM, John Lister wrote:
>>>
>>>> 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?
>>
>> yes, it is.
>>
>>> I'm assuming that your main data array is just 2 15k sas drives,
>>
>> correct
>>
>>> are you putting the WAL on the data array or is that stored somewhere else?
>>
>> pg_xlog is placed in the data array.
>>
>>> Can I ask what scaling params,
>>
>> sure, I've initialized pgbench db issuing:
>>
>> pgbench -i -s 10 pgbench
>>
>>> 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)
>>
>> those are non default values in postgresql.conf
>>
>> listen_addresses = '*'
>> max_connections = 100
>> shared_buffers = 3200MB
>> work_mem = 30MB
>> maintenance_work_mem = 800MB
>> synchronous_commit = off
>> full_page_writes = off
>> checkpoint_segments = 40
>> checkpoint_completion_target = 0.9
>> random_page_cost = 3.5
>> effective_cache_size = 10GB
>> log_timezone = 'localtime'
>> stats_temp_directory = 'pg_stat_tmp_ram'
>> autovacuum_naptime = 5min
>>
>> and then OS tweaks:
>>
>> HT bios disabled
>> /sbin/blockdev --setra 8192 /dev/sdb
>> echo deadline > /sys/block/sdb/queue/scheduler
>> vm.swappiness=0
>> vm.overcommit_memory=2
>> vm.dirty_ratio=2
>> vm.dirty_background_ratio=1
>> kernel.shmmax=3454820352
>> kernel.shmall=2048341
>> $PGDATA is on xfs (rw,noatime)
>> tmpfs on /db/9.2/pg_stat_tmp_ram type tmpfs (rw,size=50M,uid=1001,gid=1001)
>> kernel 3.2.0-32-generic
>>
>>
>> Andrea
>>
>>
>
>


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