| From: | Marinos Yannikos <mjy(at)geizhals(dot)at> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Sudden drop in DBb performance |
| Date: | 2011-09-12 23:11:12 |
| Message-ID: | 4E6E9190.4050005@geizhals.at |
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| Thread: | |
| Lists: | pgsql-performance |
Hi,
On 03.09.2011 09:26, Gerhard Wohlgenannt wrote:
> Activating log_min_duration shows for instance this query --- there are
> now constantly queries which take absurdely long.
2 things you should check:
- if your /var/lib/postgresql is on an ext3 fs, I've seen such things
before due to the changes around Linux 2.6.2X that caused long stalls
during fsync() (see https://lwn.net/Articles/328363/ etc.). But if all
your queries take longer than they should and not only a few, that
probably isn't the reason.
- regarding your hardware RAID-5, I've seen some controllers switch the
write cache off quietly for various reasons (battery too old, issues
with disks). Check if it is still enabled, without write caching
enabled, most RAID-controllers will just suck.
Regards,
Marinos
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