Re: Log shipping in v8.4.7

From: Christoph Moench-Tegeder <cmt(at)burggraben(dot)net>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: Log shipping in v8.4.7
Date: 2017-08-27 19:23:47
Message-ID: 20170827192346.x2fg3pif2ip4bydo@squirrel.exwg.net
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## Ron Johnson (ron(dot)l(dot)johnson(at)cox(dot)net):

> Everything I've read says that you should use "rsync -a". Is there
> any reason why we can't/shouldn't use "rsync -az" so as to reduce
> transfer time?

On today's LANs, total archiving time is dominated by connection
startup time (how long does it take to transfer 16MB on a 10GbE link?
See...). That's even worse when using rsync via ssh transport without
ssh's connection multiplexing - key exchange and authentication
can easily take longer than the data transfer. Compression won't
save you much time, but sure won't break anything either (but
it will take some amount of CPU time).
On really slow links, your mileage may vary.

> Also, does that change require a full restart (difficult with
> production systems)?

Even in 8.4 archive_command is marked PGC_SIGHUP, so a reload
will be sufficient. The sample configuration and perhaps pg_settings
(can't remember how informative that was back then) should
tell you the same.

Regards,
Christoph

--
Spare Space.

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