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

Tue Dec 6 18:16:37 UTC 2005
Jonathan Darton <jdarton at ibigroup.com>

>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.


AJ Darton, B.COMM CIS
System Consultant