[rdiff-backup-users] [PATCH] Sparse file support

[Eric Wheeler]

Hello all,

Please consider this patch for inclusion to the next major rdiff-backup
release.  This is my first patch submission to rdiff-backup, so please
offer constructive comments if this patch needs adjusted.

Many people have been interested in sparse file support, and so have
I---so here's the patch! 

+ Blocks that are "Globals.blocksize"-length of all \x00's are made
sparse automatically. (Globals.blocksize is currently 128k)

+ This feature has been requested a few times, and I have added
documentation to the SparseFiles wiki page:
  http://wiki.rdiff-backup.org/wiki/index.php/SparseFiles

+ Any filesystem that can f.seek() beyond EOF and f.write() to generate
sparse files is supported.  

+ This works for both local-copy and remote backups.

+ Works in conjunction with BlockFuse to backup sparse LVM snapshots:
http://www.globallinuxsecurity.pro/blog.php?q=rdiff-backup-lvm-snapshot

+ I am using this patch in production with ~600GB sparse LVM snapshots.

+ Backups of sparse files can be 2x faster since the filesystem returns
a zero-filled buffer on f.read()---rather than hitting the disk and
causing unnecessary IO.

Feedback and comments are appreciated!

Cheers,


-- 
Eric Wheeler
President
eWheeler, Inc.
  dba Global Linux Security

www.GlobalLinuxSecurity.pro
503-330-4277
PO Box 14707
Portland, OR 97293

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