Re: Postgres, fsync and RAID controller with 100M of internal cache & dedicated battery

On 8/22/07, Dmitry Koterov  wrote:
> Hello.
> You see, 50M block was fsynced for 0.25 s.
>
> The question is: how to solve this problem and make fsync run with no delay.
> Seems to me that controller's internal write cache is not used (strange,
> because all configuration options are fine), but how to check it? Or, maybe,
> there is another side-effect?

I would suggest that either the controller is NOT configured fine, OR
there's some bug in how the OS is interacting with it.

What options are there for this RAID controller, and what are they set
to?  Specifically, the writeback / writethru type options for the
cache, and it might be if it doesn't preoprly detect a battery backup
module it refuses to go into writeback mode.