[CentOS] RE: Keeping data on 2 servers in sync !

Wed Dec 7 17:38:23 UTC 2005
Matt Morgan <minxmertzmomo at gmail.com>

On 12/6/05, Jonathan Darton <jdarton at ibigroup.com> wrote:
> >I want to build 2 servers (both running samba) to provide file storage to 2
> >offices (approx 100 miles apart, linked via DSL) but all data writen to 1
> >server must also be saved to the other server.
> >Both servers would also allow users to access the data via a VPN thus
> >allowing 1 office with a failed server to access the other server via the
> >vpn and still see the data from both offices.
> >I currently have 1 server working but we want to add the second office to
> >the system. (Currently 1 office has 10 users and the second office has 1
> >user connected via VPN ) but the second office will have 20 within 12
> months
> >and the first will have 35 soon ))
>
> >Has anyone done anything like this ?
>
> I am currently synchronizing multiple office locations using a program
> called unison. Unison (http://www.cis.upenn.edu/~bcpierce/unison/) is a very
> well written program that can perform 2 way file synchronization. There are
> many configurable options with unison and I recommend that you check it out.
> In each office I have a PII350 128RAM Fedora or CentOS server running unison
> and the files are accessed via samba. I also configure samba to hide (veto)
> all of the temporary files used during synchronization. For redundancy I
> place a slave server with each master server that backs up all the user data
> / file system using rsync. This way if one of my $5 PII servers catches fire
> I can automatically switch over with no downtime for the users.
>
> The only downfall I have encountered is with Autocad files not properly
> reading the synchronized .dwl lock file and more than one user working on
> the same file. As a work around for this I have configured Unison to keep a
> backup of the last 20 versions of a file. This way I can always hit my
> backups to retreive lost data. As a side note, if anyone knows a work around
> for the stubborn autocad dwl lock file let me know :))!
>
> In any case my implementation has allowed me to synchronize file systems
> between 4 offices (3 in Canada, 1 in USA), using recycled hardware that was
> otherwise going to be donated/trashed.
>
> Let me know if you have any further questions.

I'm about to do a Unison setup on two CentOS servers, so I'm thrilled
to see this response. I also work with Architects sometimes, so I'm
interested to hear about the dwl lock file issue.

My one compound question: how are you invoking Unison? In batch mode,
with cron? How often? Wat other options did you consider before
settling on the scheme you use?

Thanks!