You have an advantage with a distributed system -- it's totally feasible to migrate between filesystems / tunings after you get started. I highly recommend usi

You have an advantage with a distributed system -- it's totally feasible to migrate between filesystems / tunings after you get started. I highly recommend using netboot and an NFS root filesystem for the storage nodes. RHEL4 is going to be a thorn in your side if you ever want to try ext4 or btrfs. Even if you stick with the mature filesystems, VFS improvements in newer kernels will give you a performance boost.