Re: Streaming base backups

On 9.1.2011 10:44, Magnus Hagander wrote:
> On Sun, Jan 9, 2011 at 09:55, Hannu Krosing  wrote:
>> On 7.1.2011 15:45, Magnus Hagander wrote:
>>> On Fri, Jan 7, 2011 at 02:15, Simon Riggs    wrote:
>>>
>>>> One very useful feature will be some way of confirming the number and
>>>> size of files to transfer, so that the base backup client can find out
>>>> the progress.
>>> The patch already does this. Or rather, as it's coded it does this
>>> once per tablespace.
>>>
>>> It'll give you an approximation only of course, that can change,
>> In this case you actually could send exact numbers, as you need to only
>> transfer the files
>>   up to the size they were when starting the base backup. The rest will be
>> taken care of by
>>   WAL replay
> It will still be an estimate, because files can get smaller, and even
> go away completely.
Sure. Just wanted to remind the fact that you don't need to send the 
tail part of the
file which was added after the start of backup.

And you can give the "worst case" estimate for space needed by base backup.

OTOH, streaming the WAL files in parallel can still fill up all 
available space :P

> But we really don't need more than an estimate...
>
Agreed.

-- 
--------------------------------------------
Hannu Krosing
Senior Consultant,
Infinite Scalability&  Performance
http://www.2ndQuadrant.com/books/