The 2.5GB -> 50MB "problem" could mean a number of things. It could also mean nothing at all. It's much more about the amount of swap (paging) space that's being used at the time of the slowdown. The fact that it runs fine for a few hour then degrades significantly would point me in the direction of watching paging space consumption. You may have added just one too many rows, making one query just big enough to make your server start paging more than it ever used to do. Check your vmstat and iostat information at the time of the slowdown, and see if you can determine whether you're paging or waiting on storage. I suspect you'll find that throwing hardware (memory, as a guess) at this problem will solve it. -----Original Message----- From: S Arvind [mailto:arvindwill@xxxxxxxxx] Sent: Monday, September 21, 2009 2:19 PM To: Scott Whitney; pgsql-admin Subject: Re: Postgres restart Thanks Scott. 1. Well, is this a dedicated database server? YES, it runs only Postgres with some Back-up script for that DBs alone daily. 2. What O/S? CentOS (Linux version 2.6.18-8.1.4.el5 (mockbuild@xxxxxxxxxxxxxxxxxxx) (gcc version 4.1.1 20070105 (Red Hat 4.1.1-52)) ) 3. What version of PG? 8.3.7 4. Have you check out memory usage? When rebooted it has more then 2.5 GB free space but after few hours it will reach 50MB. This is usual in our DB server, since this decrease never affected our performance for past years. And also for 5 months we never rebooted our system and also we had restart the postgres likely once in a month, before this problem. 5. Also, when was the last time you vacuumed the database(s)? As per advise from postgres team we are running full vaccum for every week and frequently-used table(30) vacum daily. We have nearly 640 tables in each DB. 6. Is auto-vac on? Yes ( postgres: autovacuum launcher process running) Is our problem is identifiable, from infrastructure side? -Arvind S "Many of lifes failure are people who did not realize how close they were to success when they gave up." -Thomas Edison On Mon, Sep 21, 2009 at 11:33 PM, Scott Whitney <swhitney@xxxxxxxxxxx> wrote: There's an awful lot of information left out that would be very useful to help advise you. Restarting the postgres services on a daily basis is certainly nothing that's going to corrupt your data or hurt your system, PROVIDED that it is done correctly (ie: not killing the backend postmaster when something is happening, not hard-booting the system while a RAID card is trying to write its cache, etc.) However, I think you'd be postponing the problem. The better answer might be to define and resolve the issue. "Its performance is good but gradually going down?" Well, is this a dedicated database server? What O/S? What version of PG? Have you check out memory usage? 4GB seems a bit low for the amount of data you're using. In a similar environment, I've got 12GB, and from time to time I'm paging. If "nothing changed" (TRULY, that is), you're most likely finding that you're either CPU, memory, or I/O bound, and the most likely culprits are the last 2 unless you've suddenly started some massive queries that didn't happen a few weeks ago. Also, when was the last time you vacuumed the database(s)? Is auto-vac on? I know, I know, I'm not _supposed_ to have to perform a full vacuum and analyze on my databases with auto-vac on, but if I don't, I run into performance problems, so I do that once per week, myself. -----Original Message----- From: pgsql-admin-owner@xxxxxxxxxxxxxx [mailto:pgsql-admin-owner@xxxxxxxxxxxxxx] On Behalf Of S Arvind Sent: Monday, September 21, 2009 12:46 PM To: pgsql-admin Subject: Postgres restart Recently due to some problem(not yet diagnosed) , our DB server Postgres is getting very slow after few hours. We didnt changed any settings for 6 months , so we dont know y its happening suddenly in this week. Our data folder is 118GB with 160 DBs. System is 2 Quad core with RAM 4GB. In last two days when it was restarted its performance is good but gradually going down. So few planned to restart the posgres process daily. Is it advisable to restart server daily ? since daily we can have 30 mins downtime. Please advise is it advisable or not? -Arvind S "Many of lifes failure are people who did not realize how close they were to success when they gave up." -Thomas Edison -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
