[Announce] bup 0.09: git-based backup system for really huge datasets

[Avery Pennarun]

Hi all,

bup is a file backup tool based on the git packfile format.  If you're
interested in git, you might find bup interesting because:

- It can handle really massive datasets (hundreds of gigabytes)
without melting down.

- It can handle huge individual files (hundreds of gigabytes), such as
virtual machine images or giant textual database dumps, while neither
wasting disk space nor bogging down in xdelta.

- It can backup files directly to a remote server, without creating
git objects on the local system first.

- It uses a different format for its index file (.bup/bupindex) that
allows you to search and iterate non-linearly.  Thus if you have a
filesystem with a million files and only one of them is marked dirty,
bup can back it up near-instantly.

- Like git, it separates the concept of indexing the filesystem from
the concept of actually making new commits.  Thus it would be easy to
plugin an inotify-like system eventually, avoiding the slow filesystem
iteration every time you want to make a backup.

- It introduces a "multi-index" file (midx) that has a sorted list of
the objects from multiple .pack files, so that checking for a
nonexistent object only needs to swap in two pages at most.  (This is
unimportant in git, but critical when most of your work is ingesting
huge files whose sha1sums haven't been seen before.)

- It provides a FUSE-based filesystem so that you can easily browse
your backup history, including exporting it via samba if you want.

bup doesn't yet back up extra file metadata (beyond what git already
tracks).  Obviously this will be needed relatively soon.

bup is still pretty experimental, but it's already a useful tool for
backing up your files, even if those files include millions of files
and hundreds of gigs of VM images.

You can find the source code (and README) at github:

    http://github.com/apenwarr/bup

To subscribe to the bup mailing list, send an email to:

    bup-list+subscribe at googlegroups.com

Looking forward to everyone's feedback.

Have fun,

Avery
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