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

Thu Dec 8 03:31:09 UTC 2005
Matt Morgan <minxmertzmomo at gmail.com>

On 12/7/05, Denis Croombs <denis at croombs.org> wrote:
> 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?
>
> I see the project is no longer supported, do you have rpms for it ?
>
> Thanks

It's not that it's no longer supported, really, just that the project
that initiated it is not an officially-funded academic project. It has
actually been updated since the termination of the project, it looks
like.

I haven't installed it on CentOS yet but I got FC4 rpms from fedora
extras (I just typed 'yum install unison' and it worked). I think it's
in pretty common usage in RHEL too, so it can't be too hard to find
for CentOS, right? (But let us know what you turn up :-)).