What are acceptable/reasonable/best ways to provide large, growable, shared storage at AWS, exposed as a single filesystem?

We're currently making 1TB EBS volumes ~biweekly and NFS exporting with no_subtree_check and nohide. In this setup, distinct exports appear under a single mount on the client. This arrangement does not scale well.

The options we've considered:

• LVM2 with ext4. resize2fs is too slow.
• Btrfs on Linux. not obviously ready for prime time yet.
• ZFS on Linux. not obviously ready for prime time yet (although LLNL uses it)
• ZFS on Solaris. future of this combo is uncertain (to me), and new OS in the mix
• glusterfs. heard mostly good but two scary (and maybe old?) stories.

The ideal solution would provide sharing, a single fs view, easy expandability, snapshots, and replication.

Thanks for sharing ideas and experience.