[clug] Rsync Diffs

Paul Harvey csirac2 at gmail.com
Tue Aug 4 04:16:14 UTC 2015

For what it's worth, this is exactly the use-case for copy-on-write
filesystems such as btrfs and ZFS (i.e. snapshots).

Individual machines may keep accumulating snapshots locally, while you
randomly and asynchronously transfer those snapshots to multiple other
filesystems (remote, portable, whatever) at any frequency you like.

The bonus is that these are extremely efficient - snapshots take
milliseconds to create, and btrfs|zfs send/receive are even more
efficient than rsync.

If there's interest I could do another talk on btrfs & zfs one day, I
think these are hugely under-appreciated technologies :D

On 3 August 2015 at 15:57, Brett Worth <brett.worth at gmail.com> wrote:
> Hi All.
> While we're on the topic of backups, I have a question.
> Here's a hypothetical configuration:
> SystemA  2 x data disks DiskA and DiskB
> SystemB  1 x data disk DiskZ
> These two machine start life connected to the same network and I use rsync
> to make DiskA, DiskB and DiskZ identical.
> I then send SystemB to a remote place where there is no Internet access.
> There is however a mail service.
> I make changes only to DiskA during the work day and wish to have these
> changes periodically reflected on DiskZ.  Each day I can run a task that
> sync's DiskA to DiskB.
> Is there any way I can capture the changes made to DiskB in such a way that
> I could put that information on a CD/DVD and post it to the location of
> SystemB so that someone could then apply the same changes to DiskZ?
> This could be done using find/tar and some sort of timestamp system but I
> was wondering if there could be a more elegant way to do it.  Perhaps by
> capturing something from rsync?
> Regards
> Brett
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