Re: Listing the deltas

[Ted Unangst <tedu@tedunangst.com>]

On Wed, Jun 06, 2012 at 20:24, Colin Percival wrote:
> On 06/06/12 05:19, Tom Limoncelli wrote:
>> On a machine where very little changes each day, there always seems to
>> be 20 MB of "new data".  Is there a way to list which files changed
>> and were backuped?
> 
> No.  The way the tarsnap code works internally, it generates a complete
> archive and then figures out which blocks duplicate data previously
> uploaded; the deduplication code doesn't have any way of knowing which
> files data originally belonged to (and in fact there will be blocks
> with data aggregated from multiple files).

If I remember correctly, tarsnap is only looking at aligned blocks,
too.  And is the block size 8k?  (As I recall, prepending 4k of new
data to an existing 8k file will result in 12k of new data, since the
already uploaded data does not match the new file's block alignment.)

If that's the case, it may be helpful to order the files in the
archive so that the changing files are all at the end (but being
careful to preserve file order between backups).