Laptop/Server Data Synchronization?

gbr writes "I've been trying to automatically synchronize data between a laptop and a server. When the laptop is connected to the network, I want all writes to automatically propagate across to the server. When the laptop is disconnected I want the laptop user to continue working with the local data. When the laptop is reconnected, I want the data to automatically re-sync. The issue is, the data on the server may have changed as well, which needs to propagate back to the laptop. The data doesn't contain anything too special, no database tables etc. It does contain binary data such as executables and word processing documents. I've looked at ChironFS, Unison file sync, and drbd. ChironFS needs a manual rebuild if a connection fails, and the user needs to know which machine contains the correct data. Unison requires the user to initiate the synchronization process manually every time, and drbd is just not meant for the job at hand. How do you automatically, and invisibly to the user (except in the case of conflicts), synchronize between a laptop and a server?"

Comments

rsync

[jshriverWVU]

I do this often and rsync is wonderful for such a task.

Re:rsync

[Roarkk]

rsync is part of the answer. If you're looking for a way to have multiple, incremental backups of laptops with unpredicatable patterns of connecting to the network, BackupPC is the way to go.

BackupPC is a high-performance, enterprise-grade system for backing up Linux and WinXX PCs and laptops to a server's disk. BackupPC is highly configurable and easy to install and maintain. Given the ever decreasing cost of disks and raid systems, it is now practical and cost effective to backup a large number of machines onto a server's local disk or network storage. This is what BackupPC does. For some sites, this might be the complete backup solution. For other sites, additional permanent archives could be created by periodically backing up the server to tape. A variety of Open Source systems are available for doing backup to tape. BackupPC is written in Perl and extracts backup data via SMB using Samba, tar over ssh/rsh/nfs, or rsync. It is robust, reliable, well documented and freely available as Open Source on SourceForge.
By using pooling and compression, one client of mine is using BackupPC to backup over 1TB of data distributed among over 100 laptops to a 200GB filesystem on a central server. The network is polled every hour, and any system that hasn't been backed up in the last 24 hours is queued. Beautiful system.

Re:rsync

[frenetic3]

Take a look at Dropbox (http://getdropbox.com/; screencast at http://getdropbox.com/u/2/screencast.html) if you want something that's rsync-like but integrated into Windows and OS X. It's in beta (and full disclosure: I co-founded the company) but was designed precisely because there's nothing out there that does this well and is easy to use.

In OSX, portable home directories

[shamborfosi]

I have OSX laptops using portable home directories to do exactly what you are asking for.. a network home directory that is automagically sync'd to my laptop (thus making it portable). It works both ways, and I'm definitely happy with it. I'm not sure which OS you're using though. I wrote about how to do it in an article: Full Stack: Portable Home Directory over NFS on OSX authenticated via OpenLDAP on Debian Linux if you're interested. I also just got everything to work over AFP to an OSX server running open directory as well.. but haven't had time to write it up yet (btw, a lot fewer steps).

Re:Windows & Make Available Offline

[Techman83]

A great solution till it breaks... believe me it does break and when it does be prepared for heartache. There are ways to recover it, but I think it assumes to much and the potential to screw up is a big risk. There were several users at my place of employment that found out this the hard way and now we ban the usage of it. It's not so much finding the best tool, but managing the process overall and how to do that.. Well we are still in the process of developing that one!