Redundant Data storage solutions (Data clusters?)

[Lamp Zy]

Hi,

What I'm looking for is suggestions, best practices, success stories or 
anything that will point me in the right direction.

I realize that our requirements are the same as 90% of the companies out 
there but the "Redundancy" part is where I stumbled upon.

We are hosting user images that are less then 1MB in size. Images are 
small and the processing we are doing on them is not I/O intensive so 
there is no need for high performance hardware or high network speeds. 
File systems are exported to the application servers over NFS.

All we need is a reliable storage solution that works over NFS (NAS).

It is expected that our storage needs will grow to about 50+ TB within 5 
years.

One of the requirements is redundancy. If one storage unit fails then 
another should pick up with no interruption. Also it needs to be 
scalable. At this point we can not invest in all 50TB storage so we need 
to be able to add more storage easily as needed.

We are about to go with gluster (gluster.org). It is a Data Cluster 
solution where one can add systems with DAS in pairs. Each pair can be 
configured to simulate RAID1 (if I understand correctly). Looks good... 
on paper at least. My concerns are that they use their own glusterFS 
which probably relies on ext3 or zfs. Also you can use NFS but it's 
recommended to use their client daemon instead and so on.

Any recommendation about a solution or suggestions are highly appreciated.

Thanks
Peter