From: Dianne Skoll <dfs@roaringpenguin.com>
To: pgsql-admin@lists.postgresql.org
Subject: Re: Reliable WAL file shipping over unreliable network
Date: Wed, 28 Feb 2018 13:26:20 -0500
Message-ID: <20180228132620.2c882f84@hydrogen.roaringpenguin.com> (raw)
In-Reply-To: <37C5A42B-4CDD-4F01-8F1E-1B185C1819B9@icloud.com>
References: <dd116172-3ddf-ee56-57f3-6e18d49abf8e@shopzeus.com>
<400AC9CD-1E43-422C-A689-70BDBAFF231E@elevated-dev.com>
<ee3ae4be-ab24-8443-82c1-95bcd4f86a63@shopzeus.com>
<debd4205-e27a-cd9d-9169-6748e65083a2@shopzeus.com>
<BA4A1866-95B0-49C6-8CD1-3D1B60A7837E@elevated-dev.com>
<CF30D15A-BD42-42A7-9AD3-BB69AF9E8047@icloud.com>
<D5B11CF5-E816-435B-BFB8-1226E23C046A@elevated-dev.com>
<37C5A42B-4CDD-4F01-8F1E-1B185C1819B9@icloud.com>
On Wed, 28 Feb 2018 13:15:48 -0500
Rui DeSousa <rui.desousa@icloud.com> wrote:
> Sure it does… what happens if the archive server gets full? There is
> a situation that can fool rsync into thinking it was successfully
> transferred as rsync only relies on filesystem metadata to verify the
> file is different.
That's incorrect. The original transfer will fail and rsync will remove
the temporary file. It doesn't rename the file to the final destination
until and unless the transfer is successful.
"-c" is only used for files that might change multiple times per second;
since most file systems have only 1-second granualarity in file timestamps,
you can't rely on a file being identical if the size and timestamps are the
same.
> The “-c” option will validate the file using a checksum and not just
> rely on just filesystem metadata.
That's incorrect. "-c" applies only when rsync looks at existing files
to see if they differ. It does not affect what happens when rsync actually
copies the file data over; that's always verified with a checksum.
Regards,
Dianne.
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To: pgsql-admin@postgresql.org
Cc: dfs@roaringpenguin.com, pgsql-admin@lists.postgresql.org
Subject: Re: Reliable WAL file shipping over unreliable network
In-Reply-To: <20180228132620.2c882f84@hydrogen.roaringpenguin.com>
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