some thoughts about gmirror

[Mike Wolman]

>  if you were keeping track of the blocks which had changed
>  then you do not need to generate this list and simply send over the
>  changed blocks.
>
> Unison keeps a list of files at each end and only exchanges block lists for
> files that have changed.  I use it to sync 40GB (10K files) over a 1Mbps
> link and it's very fast.  It also will do two-way sync.
>

Unison and rsync both work on the filesystem level and not with
the blocks directly so would not be able to achieve the same result
as the live network backup on netbsd - ie allowing a simple dd
restore of a machine.

As this would be filesystem independent and if you are running zfs or 
other snapshot capable filesystem i think rsync or unison would have a 
problem working with the snapshots.  i do use rsync with close to about 
1Tb of data and a lot hard links for - but if the remote file changes you 
have to store the entire copy of new file and not just the actual blocks 
which have changed.

Mike.

On Sat, 7 Apr 2007, Jim Rees wrote:

> Mike Wolman wrote:
>
>