Re: performance on new linux box

On Wed, Jul 7, 2010 at 4:06 PM, Ryan Wexler <ryan(at)iridiumsuite(dot)com> wrote:
> Postgresql was previously running on a single cpu linux machine with 2 gigs
> of memory and a single sata drive (v8.3).  Basically a desktop with linux on
> it.  I experienced slow performance.
>
> So, I finally moved it to a real server.  A dually zeon centos machine with
> 6 gigs of memory and raid 10, postgres 8.4.  But, I am now experiencing even
> worse performance issues.
>
> My system is consistently highly transactional.  However, there is also
> regular complex queries and occasional bulk loads.
>
> On the new system the bulk loads are extremely slower than on the previous
> machine and so are the more complex queries.  The smaller transactional
> queries seem comparable but i had expected an improvement.  Performing a db
> import via psql -d databas -f dbfile illustrates this problem.  It takes 5
> hours to run this import.  By contrast, if I perform this same exact import
> on my crappy windows box with only 2 gigs of memory and default postgres
> settings it takes 1 hour.  Same deal with the old linux machine.  How is
> this possible?
>
> Here are some of my key config settings:
> max_connections = 100
> shared_buffers = 768MB
> effective_cache_size = 2560MB
> work_mem = 16MB
> maintenance_work_mem = 128MB
> checkpoint_segments = 7
> checkpoint_timeout = 7min
> checkpoint_completion_target = 0.5
>
> I have tried varying the shared_buffers size from 128 all the way to 1500mbs
> and got basically the same result.   Is there a setting change I should be
> considering?
>
> Does 8.4 have performance problems or is this unique to me?
>
> thanks
>
>

I think the most likely explanation is that the crappy box lied about
fsync'ing data and your server is not. Did you purchase a raid card
with a bbu? If so, can you set the write cache policy to write-back?

--
Rob Wultsch
wultsch(at)gmail(dot)com