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Re: [linux-lvm] Using LVM snapshots for hourly backups

On 10/13/06, Roger Lucas <roger planbit co uk> wrote:
Hi Nick,

RSYNC is useful for this, but it works at the file level.  If you had, for example, a 1GB e-mail file (e.g. Outlook PST) or a large
database file, and it was getting small changes every day (e.g. receiving a dozen 10KB e-mails => 120KB of changes), then RSYNC
would quickly eat up your disk space as each backup taken with RSYNC a complete new copy of the whole 1GB file.

Cascaded LVM snapshots, on the other hand, would allow the just the changes within the files to be kept, dramatically reducing the
disk usage.

I'm sure that you know this already, but it was worth explicitly stating the difference between RSYCN and LVM snapshots in case
someone reading the list wasn't as sure.



For now, you may want to checkout rdiff-backup.  It uses rsync like
functionality to find deltas in your files and then it only backs up
the deltas.

IIRC, it actually keeps a current copy of your file, plus a series of
deltas that let you get to older versions.

Greg Freemyer
The Norcross Group
Forensics for the 21st Century

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