High Scalability Building bigger, faster, more reliable websites.

I have a few apache servers ( arround 11 atm ) serving a small amount of data ( arround 44 gigs right now ).

For some time I have been using rsync to keep all the content equal on all servers, but the amount of data has been growing, and rsync takes a few too much time to "compare" all data from source to destination, and create a lot of I/O.

I have been taking a look at MogileFS, it seems a good and reliable option, but as the fuse module is not finished, we should have to rewrite all our apps, and its not an option atm.

Any ideas?

I just want a "real time, non resource-hungry" solution alternative for rsync. If I get more features on the way, then they are welcome :)

Why I prefer to use a Distributed File System instead of using NAS + NFS?

- I need 2 NAS, if I dont want a point of failure, and NAS hard is expensive.
- Non-shared hardware, all server has their own local disks.
- As files are replicated, I can save a lot of money, RAID is not a MUST.

Thnx in advance for your help and sorry for my english :)