[NTLUG:Discuss] File Replication & 2-way Synchronization

[Stan Tigrett]

PROBLEM: We have 3 offices in different locations who need access to each of the other office's files.  The offices each run a linux/samba fileserver, with clients using win9x to connect.  Each office is connected to the internet via a ADSL line (1Mb/128kb) and run a linux firewall (a different machine than the fileserver).  One office has about 10 gigs of data, and the other two have about 2 gigs each.  The users can't handle using FTP - they will only accept a 'new drive mapping' in windows.  It is not very likely that the same file will be accessed by different users at different locations at the same time.

POSSIBLE SOLUTIONS:
1 - Mount the data remotely using NFS across the internet, using strict firewall rules to only allow exporting to the 3 office IP addresses.  Use samba to share the nfs mount to the users.
	Pros - 	Data will always be current.  Changes will occur in real time.
	Cons - 	The DSL links not very stable.  Would probably need a cron job to test the nfs connection & re-mount it if neccessary.
		Data access will be extremely slow.

2 - Use rsync to perform 2-way synchronization of the files, using the same strict firewall rules above...  Use samba to share the replicated directories.
	Pros -	Data access will be as fast as local data.
		Don't have to worry about the DSL links
	Cons - 	Data may be stale.
		Initial replication will take a long time...
		Deleting files from one server to the other...

It seems that #2 is the best solution so far, using a cron job to synchronize the files every hour or so, but I have one major caveat.  One of the accounting programs these offices use creates several temporary *.dbf files while they are working on it.  Using rsync without the --delete option would eventually leave hundreds of these files laying around.  However, if I do use the --delete option, those temp files may be deleted if a synchronization occurs while a user is still working with them. 

If there were a way to only delete files that were created BEFORE the last synchronization occured, then we would be in good shape, I think.  I haven't found any kind of option like that, though.

Any ideas? Advice? Other approaches?

Thanks -
Stan