Re: PITR with rsync

From: Steve Crawford <scrawford(at)pinpointresearch(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: David(dot)Bear(at)asu(dot)edu, pgsql-admin(at)postgresql(dot)org
Subject: Re: PITR with rsync
Date: 2007-08-07 15:37:02
Message-ID: 46B8919E.7030408@pinpointresearch.com
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> If you are going over an ssh connection then scp seems like the
> appropriate tool. Yeah, rsync would work, but it's just a useless
> extra layer of software...

Actually, rsync has one edge over scp even where its other attributes
are moot: atomicity.

Rsync keeps the data in a temporary location then moves the whole file
into place at the conclusion of a successful transfer. Scp, however,
creates the file at start of transfer and that file will continue to
grow as the transfer progresses. A failure part-way through a scp
transfer will leave an incomplete file on the receiving end.

For situations where a process on the receiving side watches for and
processes newly added files or situations where I require a reliable
all-or-none transfer such as distribution of configuration files, I use
rsync.

Of course this attribute of rsync means that updates of an existing file
require sufficient disk-space for both old and new versions of the file.

Cheers,
Steve

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