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From Mark Montague <>
Subject Re: [users@httpd] syncing across web cluster
Date Mon, 23 Jan 2012 14:56:37 GMT
On January 23, 2012 9:35 , Roland RoLaNd <> wrote:
> i've successfully setup web clustering between 7 web servers.

How did you set up clustering?  There are several ways, and which one 
you chose can affect the answer to your question below.

> now i'm having a prob where a user uploads a file, and it only exists 
> on the server that his session landed on.
> I'm seeking your help in possible ways to propagate files uploaded 
> across servers.

Let's assume your web servers are running under Linux.

The easiest way (ignoring what you've already done to set up clustering) 
is to use NFS to share the document root directories for your web 
virtual hosts and/or to share the upload directories.  That is, one of 
your machines will be a fileserver and export these directories to all 
of the other web servers in your cluster.  If you need fault tolerance, 
you can have multiple front-end servers with heartbeat and automatic 
failover, possibly backed by a SAN.

Another option is to have all web servers in your cluster periodically 
(say, once every 5 minutes) synchronize their upload directories with 
one another -- or, better and easier, a central host -- via rsync.

What may be the best way is to not store the files in a filesystem, but 
instead store them in a database -- preferably a NoSQL database such as 
MongoDB or Cassandra -- so that all web servers can access them.  This 
would require changing any script that uses the uploaded files to 
retrieve them from the database instead of from the filesystem.

   Mark Montague

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