Re: [PATCHES] Doc update for pg_start_backup

[Heikki Linnakangas <heikki(at)enterprisedb(dot)com>]

Tom Lane wrote:
> Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> > Added a note to the docs that pg_start_backup can take a long time to 
> > finish now that we spread out checkpoints:
>
> I was starting to wordsmith this, and then wondered whether it's not
> just a stupid idea for pg_start_backup to act that way.  The reason
> you're doing it is to take a base backup, right?  What are you going
> to take the base backup with?  I do not offhand know of any backup
> tools that don't suck major amounts of I/O bandwidth.  

scp over a network? It's still going to consume a fair amount of I/O, 
but the network could very well be the bottleneck.

> That being
> the case, you're simply not going to schedule the operation during
> full-load periods.  And that leads to the conclusion that
> pg_start_backup should just use CHECKPOINT_IMMEDIATE and not slow
> you down.

That's probably true in most cases. But on a system that doesn't have 
quite periods, you're still going to have to take the backup.

To be honest, I've never worked as a DBA and never had to deal with 
taking backups of a production system, so my gut feelings on this could 
be totally wrong.

--
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com