| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | David Fetter <david(at)fetter(dot)org>, marcin mank <marcin(dot)mank(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Allowing multiple concurrent base backups |
| Date: | 2011-01-12 15:24:31 |
| Message-ID: | 26036.1294845871@sss.pgh.pa.us |
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Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> On 12.01.2011 17:15, David Fetter wrote:
>> On Wed, Jan 12, 2011 at 10:26:05AM +0100, marcin mank wrote:
>>> Considering that parallell base backups would be io-bound (or
>>> network-bound), there is little need to actually run them in parallell
>>
>> That's not actually true. Backups at the moment are CPU-bound, and
>> running them in parallel is one way to make them closer to I/O-bound,
>> which is what they *should* be.
> That's a different kind of "parallel". We're talking about taking
> multiple backups in parallel, each using one process, and you're talking
> about taking one backup using multiple parallel processes or threads.
Even more to the point, you're confusing pg_dump with a base backup.
The reason pg_dump eats a lot of CPU is primarily COPY's data conversion
and formatting requirements, none of which will happen in a base backup
(streaming or otherwise).
regards, tom lane
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