Hi,

I have a (at least for me) quite complex problem to solve:

At the moment we have 3 servers in 3 different locations, which synchronize their data at night via a rsync job.

What i would like is that the servers synchronize their filesystems in realtime and also act as a local cache for the location.

To make it a little clearer what i mean here's an example:

There are Servers A B in Location 1 2.
These 2 servers somehow (I don't know how, thats exactly my question) have their filesystems sychronized.
The server are on a 1Gbit LAN and connected to each other over a 34Mbit WAN.
The client X is in Location 1 and Y in Location 2.

Now client X in L1 uploads a huge file to Server A.
Shortly after the upload is finished, client Y in L2 wants to download this file from Server B. Server B is not yet finished with the synchronization and should transparently now get the file from Server A and serve it to the client while continuing the synchronization.
Of course this transfer is slow for Client Y cause he effectively only has 34mbit - but at least he doesn't have to worry about which server to get the file from.
After some time then the servers are 100% synchronized again and all clients get their LAN bandwidth.


Is there any software / filesystem / cluster solution / whatever that you know of that does exactly this?

I bet EMC has something shiny expensive for fast mirroring like Symetrix + SRDF. I don't know if it works via WAN though.

Hi,

Please monitor I/O activity and CPU utilization of both servers. If the hardware and configuration of both servers are identical, then Network would be the bottleneck.

Is it not possible to use file server and mount the file system on each server so that uploading/downloading get effect immediately into all servers?

Regards!

The problem is i can not use a centralized server for performance reasons - 34mbit just isn't enough bandwith. I would have to use a fileserver in each location and that would not realy help as i would have the problem of keeping them in sync again.
The data of the servers is mostly used on the server it is stored, but if a user wants to access a file that is not on his server he has to wait a day at the moment - or copy it manually.

Have you tried Unison before, and does it meet your needs (or at least most of them)?

Unison File Synchronizer

Unison is what i use at the moment, but there has to be something like DFS (windows) for Unix/Linux