On Thu, Jul 3, 2014 at 2:06 PM, <m.roth@xxxxxxxxx> wrote:
> Lists wrote:
>> On 07/02/2014 12:57 PM, m.roth@xxxxxxxxx wrote:
>>> I think the buzzword you want is dedup.
>> dedup works at the file level. Here we're talking about files that are
>> highly similar but not identical. I don't want to rewrite an entire file
>> that's 99% identical to the new file form, I just want to write a small
>> set of changes. I'd use ZFS to keep track of which blocks change over
>> time.
>>
>> I've been asking around, and it seems this capability doesn't exist
>> *anywhere*.
>
> I was under the impression from a few years ago that at least the
> then-commercial versions operated at the block level, *not* at the file
> level. rsync works at the file level, and dedup is supposed to be fancier.
>
Yes, basically it would keep a table of hashes of the content of
existing blocks and do something magic to map writes of new matching
blocks to the existing copy at the file system level. Whether that
turns out to be faster/better than something like rdiff-backup would
be up to the implementations. Oh, and I forgot to mention that there
is an alpha version of backuppc4 at
http://sourceforge.net/projects/backuppc/files/backuppc-beta/4.0.0alpha3/
that is supposed to do deltas between runs.
But, since this is about postgresql, the right way is probably just to
set up replication and let it send the changes itself instead of doing
frequent dumps.
--
Les Mikesell
lesmikesell@xxxxxxxxx
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