Re: Linux filesystem performance and checkpoint sorting

Josh Berkus wrote:
> So: Linux flavor?  Kernel version?  Disk system and PG directory layout?
>   

OS configuration and PostgreSQL settings are saved into the output from 
the later runs (I added that somewhere in the middle):

http://www.2ndquadrant.us/pgbench-results/294/pg_settings.txt

That's Ubuntu 10.04, kernel 2.6.32. 

There is a test rig bug that queries the wrong PostgreSQL settings in 
the later ones, but they didn't change after #294 here.  The kernel 
configuration stuff is accurate through, which confirms exactly what 
settings for the dirty_* parameters was effective for each during the 
tests I was changing those around.

16GB of RAM, 8 Hyperthreaded cores (4 real ones) via Intel i7-870.  
Areca ARC-1210 controller, 256MB of cache.

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda1              40G  7.5G   30G  20% /
/dev/md1              838G   15G  824G   2% /stripe
/dev/sdd1             149G  2.1G  147G   2% /xlog

/stripe is a 3 disk RAID0, setup to only use the first section of the 
drive ("short-stroked").  That makes its performance a little more like 
a small SAS disk, rather than the cheapo 7200RPM SATA drives they 
actually are (Western Digital 640GB WD6400AAKS-65A7B).  /xlog is a 
single disk, 160GB WD1600AAJS-00WAA.  OS, server logs, and test results 
information all go to the root filesystem on a different drive.  My aim 
was to get similar performance to what someone with an 8-disk RAID10 
array might see, except without the redundancy.  Basic entry-level 
database server here in 2011.

bonnie++ on the main database disk:  read 301MB/s write 215MB/s, seeks 
423.4/second.  Measured around 10K small commits/second to prove the 
battery-backed write cache works fine.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books