Re: performance on new linux box

On 07/07/2010 06:06 PM, Ryan Wexler 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
>

Yeah, I inherited a "server" (the quotes are sarcastic air quotes), with really bad disk IO... er.. really safe disk IO. Try the dd test. On my desktop I get 60-70 meg a second. On this "server" (I laugh) I got about 20. I had to go out of my way (way out) to enable the disk caching, and even then only got 50 meg a second.

http://www.westnet.com/~gsmith/content/postgresql/pg-disktesting.htm

-Andy