Re: Streaming a base backup from master

On 03/09/10 18:01, Tom Lane wrote:
> Heikki Linnakangas<heikki.linnakangas@enterprisedb.com>  writes:
>> On 03/09/10 15:16, Greg Stark wrote:
>>> On Fri, Sep 3, 2010 at 12:19 PM, Heikki Linnakangas
>>> <heikki.linnakangas@enterprisedb.com>   wrote:
>>>> * We need a smarter way to do pg_start/stop_backup() with this. At the
>>>> moment, you can only have one backup running at a time, but we shouldn't
>>>> have that limitation with this built-in mechanism.
>>>
>>> Well there's no particular reason we couldn't support having multiple
>>> pg_start_backup() pending either. It's just not usually something
>>> people have need so far.
>
>> The backup label file makes that hard. There can be only one at a time.
>
> I don't actually see a use-case for streaming multiple concurrent
> backups.  How many people are going to be able to afford that kind of
> load on the master's I/O bandwidth?

It's more a matter of convenience when you're setting up test 
environments with small databases or something like that. I don't see 
many people regularly using the streaming backup for anything larger 
than a few hundred gigabytes anyway. At that point you'll most likely 
want to use something more efficient.

> Certainly for version 1, it would be sufficient to throw an error if
> someone tries to start a backup while another one is in progress.
> *Maybe*, down the road, we'd want to relax it.

Yeah, it's OK for 1st version.

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