Re: [rdiff-backup-users] Re: 1) Using samba to backup windows shares 2) sparse files

[Ben Escoto]

>>>>> "SK" == STELIOS KYRIACOU <address@hidden>
>>>>> wrote the following on Tue, 17 Jun 2003 15:27:06 -0400

  SK> I think i figured out the first part of my problem when backing
  SK> up windows files (with samba): It seems that FAT and NTFS are
  SK> not as accurate in reporting the modification date of a file so
  SK> that file is flagged as changed even though it is not changed. A
  SK> solution to this problem would be a flag to rdiff-backup similar
  SK> to rsync --modify-window to allow a 2-second difference as being
  SK> the same date.  By the way, i suggested in my first email that
  SK> the modification time was changing by 1/100 of a second; that
  SK> was a mistake: the change is 1 second.

I'm not sure I understand the problem.  If, say, we are backing up a
FAT filesystem that has coarser-grained modification times, shouldn't
that, if anything, result in files which appear to the same and
aren't, not vice-versa?

Suppose we are backing up a windows file system to a linux one.  At
time 1000000000 a file is created.  Later at time 1000000001 it gets
changed, but the time stays at 1000000000.  This could cause
rdiff-backup not to notice the file is changed.

I could see there could be a problem if we backed up a unix filesystem
onto a windows one, but that's not what you seem to be doing?

  SK> Any comments on my second question regarding rdiff-backup and
  SK> possibility of improving it to allow for sparse file checking
  SK> and subsequent sparse file writing? This would be quite useful
  SK> for saving a lot of space (20% in our lab) and more importantly
  SK> for not running out of space due to the backup taking more space
  SK> than the original (which has some sparse files).

Hmm, I haven't really looked into this, but have heard that sparse
files are a real pain.  For instance:

ftp://ftp.berlios.de/pub/star/testscripts/zwicky/testdump.doc.html

claims that there is no portable way to do this.  I wouldn't enjoy
writing a lot of C, especially if it were specific to various OSes..
But I guess if rsync does it maybe I can steal code or something.


-- 
Ben Escoto

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