First, here is the original discussion:
http://www.backupcentral.com/phpBB2/two-way-mirrors-of-external-mailing-lists-3/rdiff-backup-23/rdiff-creating-a-patch-file-when-there-are-no-changes-to-th-63313/
Second
I'm running rdiff-backup 1.2.5 on both systems. The windows system is using the native windows binary. On the windows PC, I am running rdiff-backup, using plink.exe for the remote schema, and backing up C:\\ to a folder on the linux PC.
Most of the diffs are not gzipped. I assume they were small enough that the gzip overhead would make them bigger, so somewhere something decided not to compress the files. A few of the larger files have diffs large enough to be compressed.
Using a photograph and diff that I can provide upon request, the md5sum for both the source and the destination file is 834c6f37ad3b53942d5842a97fce5df0. The hexdump of the diff is
0000000 7372 3602 0046 8008 064a 0260 4a20 6006
0000010 2002 064a 0260 4a20 e00e 4015 064a 0260
0000020 4a20 6006 2002 064a 0260 4a20 6006 2002
0000030 064a 0260 4a20 6006 2002 064a 0260 4a20
0000040 6006 2002 064a 0260 4b20 4037 0400 f85f
0000050 0000
0000051
The file is 293.8 KB.
Thanks for the help.
- Austin
PS: Andrew, sorry about the duplicate. I always forget to hit reply all and send to the list.
On Sun, Feb 1, 2009 at 9:30 AM, Andrew Ferguson
<address@hidden> wrote:
On Feb 1, 2009, at 10:23 AM, Austin Roberts wrote:
I'm doing a backup (from Windows to Linux, though I'm not sure that's relevant), and I've noticed that a lot of files (especially pictures) that haven't changed at all are being incremented. It will say "Processing changed file ..." "Incrementing mirror file ..." Even though the file hasn't changed at all. The resulting diffs are generally between 9 and 141 bytes.
In order to help you, you're going to have to describe your situation some more. What version of rdiff-backup are you running on each end? Is it the native Windows client or the Cygwin client? How are you doing the backup? If you gunzip one of the diff.gz files, what does it say? (it will be in binary, use hexdump) ... What does md5 report for the "different" files? How large are the files which are being marked as "changed"?
I found a discussion of this from 2004, and the consensus seemed to be that these were unique rsync deltas, even though the file hadn't changed. Someone fixed it by doing md5sums of the files on each side to make sure they were different before storing anything.
Can you send a link to that discussion? Given it's age, it's probably not relevant to your particular situation. The rdiff-backup code has changed a lot in the last five years.
thanks,
Andrew