Whether or not you need drbd really depends more on your requirements for data availability than on the technical details of your storage connectivity.
Arguably in most environments you don't "need" drbd; you use it to provide some level of data availability that would be difficult to achieve without it. The one exception is if you're using drbd's dual-master mode to emulate shared storage...but you say you are in an "FC environment", which I'm going to assume means your virtualization hosts have access to shared storage. Even in a SAN environment, you may end up using drbd as a remote replication solution.
You haven't provided a lot of details about your current environment, so it might be difficult to provide good recommendations. For smaller clusters, RedHat's GFS might be a good option -- if you're running on RedHat/CentOS/Fedora hosts, the packages are already available as part of the stock distribution. People also seem to be having luck with OCFS2, and the GlusterFS folks also claim their product works well for virtualization storage.
Depending on your environment, simply setting up a NFS server and accessing storage via NFS might provide acceptable performance -- and would be substantially simpler to set up than any of the clustered filesystem options.
Remember that you don't need a cluster filesystem if you don't use imagefiles. In most cases, it's far faster (and lighter on the host/Dom0 cache) to use block devices (LVs, LUNs). If you go that route, you only need cLVM or plain LUN management.
Whether or not you need drbd really depends more on your requirements for data availability than on the technical details of your storage connectivity.
Arguably in most environments you don't "need" drbd; you use it to provide some level of data availability that would be difficult to achieve without it. The one exception is if you're using drbd's dual-master mode to emulate shared storage...but you say you are in an "FC environment", which I'm going to assume means your virtualization hosts have access to shared storage. Even in a SAN environment, you may end up using drbd as a remote replication solution.
You haven't provided a lot of details about your current environment, so it might be difficult to provide good recommendations. For smaller clusters, RedHat's GFS might be a good option -- if you're running on RedHat/CentOS/Fedora hosts, the packages are already available as part of the stock distribution. People also seem to be having luck with OCFS2, and the GlusterFS folks also claim their product works well for virtualization storage.
Depending on your environment, simply setting up a NFS server and accessing storage via NFS might provide acceptable performance -- and would be substantially simpler to set up than any of the clustered filesystem options.
Remember that you don't need a cluster filesystem if you don't use imagefiles. In most cases, it's far faster (and lighter on the host/Dom0 cache) to use block devices (LVs, LUNs). If you go that route, you only need cLVM or plain LUN management.
We've used OCFS2 very successfully for a while now, I know there may be bigger/better filesystems out there but I trust OCFS2.