Re: pg_start_backup() takes too long

On Sun, 2008-09-28 at 08:35 -0700, Joshua D. Drake wrote:
> Ivan Zolotukhin wrote:
> > Hello,
> >
> > Nothing bad both in system and postgres logs :( No serious activity
> > during backup. I've had to change statement_timeout for backup user to
> > make it work. But I cannot reproduce this case unfortunately.
>
> This is actually not uncommon and PostgreSQL shows exactly nothing in
> terms of why it is taking so long. The only assumption I have come up
> with is that start_backup does cause a checkpoint.

Yes, it does a normal checkpoint and writes a file. No reason for it to
take longer than any other checkpoint.

At 8.2 and below checkpoints were frequently delayed on busy systems.
This was because of lwlock starvation during commit phase of
transactions. That was fixed in 8.3.

--
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support