Glenn, does AST pax support data deduplication, i.e. has a ustar
extension which allows that data blocks which share the same content
are only stored once?

Irek

---------- Forwarded message ----------
From: Arne Jansen <[email protected]>
Date: Fri, Oct 19, 2012 at 11:23 AM
Subject: Re: [zfs-discuss] [zfs] portable zfs send streams (preview webrev)
To: Irek Szczesniak <[email protected]>
Cc: [email protected], [email protected], Matthew Ahrens
<[email protected]>, Alexander Block <[email protected]>


On 19.10.2012 11:16, Irek Szczesniak wrote:
> On Wed, Oct 17, 2012 at 2:29 PM, Arne Jansen <[email protected]> wrote:
>> We have finished a beta version of the feature. A webrev for it
>> can be found here:
>>
>> http://cr.illumos.org/~webrev/sensille/fits-send/
>>
>> It adds a command 'zfs fits-send'. The resulting streams can
>> currently only be received on btrfs, but more receivers will
>> follow.
>> It would be great if anyone interested could give it some testing
>> and/or review. If there are no objections, I'll send a formal
>> webrev soon.
>
> Why are you trying to reinvent the wheel? AFAIK some tar versions and
> AT&T AST pax support deltas based on a standard (I'll have to dig out
> the exact specification, but from looking at it you did double work).
>

I haven't done the research myself, but the result was that pax would
have needed significant extension, but I don't have the details. If
you dig out a format already in use that supports everything we need
(like sharing data between files, needed for btrfs reflinks), it should
be easy to change the format. Stuffing the data into a specific format
is not an essential part of the work and can be changed with a limited
amount of work.

-Arne

> Irek
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