replicating data over 2 servers

[Chris Shenton]

nbari at unixmexico.com writes:

> the problem when using rsync in both servers is that if data on server A
> is  updated, and data on server B is updated at the same time, there is a
> chance to lost data.
> 
> If a user writes to a file on server A and then rsyn is executed data will
> be lost, and so if a users writees on server B an rsync tryis to fecth
> from server A data will be lost

I haven't used this yet but it sounds like it fits the bill:

  http://www.cis.upenn.edu/~bcpierce/unison/

  Unison is a file-synchronization tool for Unix and Windows. (It also
  works on OSX to some extent, but it does not yet deal with 'resource
  forks' correctly; more information on OSX usage can be found on the
  unison-users mailing list archives.) It allows two replicas of a
  collection of files and directories to be stored on different hosts
  (or different disks on the same host), modified separately, and then
  brought up to date by propagating the changes in each replica to the
  other.

  Unison shares a number of features with tools such as configuration
  management packages (CVS, PRCS, etc.), distributed filesystems
  (Coda, etc.), uni-directional mirroring utilities (rsync, etc.), and
  other synchronizers (Intellisync, Reconcile, etc). However, there
  are several points where it differs:

  [...]

It's in /usr/ports/net/unison