I wouldn't depend on your multipathing solution too much as it's not certified for this storage solution and I've been told it's known to not work 100% (of the times) when a failover were to be needed.

Another thing is that your cabling is very wrong.

The cabling should be like the picture in this link. Each switch does need to use a different subnet obviously as they are isolated (from the LAN and eachother) networks.

Are your 2 hosts setup for clustered file systems?

This guide might be of help in setting it up as a cluster:

http://linux.dell.com/wiki/index.php/Products/HA/DellRedHatHALinuxCluster

I, however, agree that dm-multipath is not supported and neither is Fedora core:).

I am not sure that it is a caching issue as much as a clustering issue.

Thanks,

Mohan

I agree with Mohan - this sounds like you need Redhat (....or Centos) and GFS if you want to share those LUNs properly. Good luck!