Re: Allowing multiple concurrent base backups

On Thu, Jan 13, 2011 at 2:19 PM, Ross J. Reedstrom <reedstrm@rice.edu> wrote:
> On Tue, Jan 11, 2011 at 11:06:18AM -0800, Josh Berkus wrote:
>>
>> > It makes it very convenient to set up standbys, without having to worry
>> > that you'll conflict e.g with a nightly backup. I don't imagine people
>> > will use streaming base backups for very large databases anyway.
>>
>> Also, imagine that you're provisioning a 10-node replication cluster on
>> EC2.  This would make that worlds easier.
>
> Hmm, perhaps. My concern is that a naive attempt to do that is going to
> have 10 base-backups happening at the same time, completely slamming the
> master, and none of them completing is a reasonable time. Is this
> possible, or is it that simultaneity will buy you hot caches and backup
> #2 -> #10 all run faster?

That's going to depend on the situation.  If the database fits in
memory, then it's just going to work.  If it fits on disk, it's less
obvious whether it'll be good or bad, but an arbitrary limitation here
doesn't serve us well.

P.S. Your reply-to header is busted.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company