Red Hat has several options for storage needs — GFS2, CIFS, (p)NFS, Gluster. It’s all about right tool for the job.
RHEL Resilient Storage – GFS2
Shared storage, scales up to 100TB per instance, supports 2-16 nodes in the cluster, x86_64 only.
Performance is directly related to server and storage class, and to access sets — best case is where each node generally access its own filesystem area, worst case is where nodes are fighting for locks of the same files/directories.
RHEL NFS Client
It’s an NFS client — what else needs to be said?
Metadata server tells you where to go to get your data, and can even reference data across multiple-tiers — NFS or directly to the SAN.
Performance can be enhanced with large write caches, internally tiered storage, and is suitable for most workloads, even transactional DBs (using O_DIRECT). Not so good for highly random read workloads.
Red Hat Storage (Gluster + utilities, support, and blueprint)
RHS is a standalone product. RHS servers in supported config are RAID6+local storage, XFS filesystems, dedicated RHEL6.x and Gluster software, all deployed on commodity hardware (reducing cost).
Clients use Gluster for scalability; NFS or CIFS for simplicity.
Performance improved by scaling horizontally across servers. But, there is no write cache, and Gluster is a user=space filesystem with some overhead from context switching. Likely not suitable for big I/O (databases, mail servers), but great for big unstructured data.
Scales to 6PB (or 3PB mirrored), and can add capacity dynamically.