I replied; should also forward to the list...

---------- Forwarded message ----------
From: Christopher Browne <cbbrowne at afilias.info>
Date: Wed, Apr 2, 2014 at 4:28 PM
Subject: Re: [Slony1-general] help tuning to reduce replication lag
To: Jeff Frost <jeff at pgexperts.com>


The 0.978 seconds is how long it took for the CURSOR to get to the point
where it was able to provide the first row.

Given that the SYNCs seem to be taking on the order of 1000 seconds, that's
not much overhead.

(In contrast, it would be distressing if it took 1219.35 seconds for the
"delay for first row", and then the SYNC was completed in another 2
seconds.)

It's taking a thousand-ish seconds to process ~200K
inserts/updates/deletes, which doesn't seem ludicrously out of line with
what I'd expect.

It doesn't seem likely to me that the amount of memory that you have is
terribly relevant to performance; the processing of a stream of 200K-ish
I/U/Ds won't be RAM-hungry, it's mostly hungry in:
a) Chewing CPU for the parsing and planning of each statement;
b) Chewing disk I/O for the processing of the I/U/Ds and logging updates in
WAL.

I would expect Slony version 2.2 to be a fair bit quicker, as it uses COPY
protocol to copy the data in, which dramatically reduces the amount of
effort that the subscriber server needs to do parsing and planning the SQL
for the INSERT/UPDATE/DELETE statements.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.slony.info/pipermail/slony1-general/attachments/20140402/4c336c77/attachment.htm