Virtual storage appliances offer great features, flexibility, and pricing, but like most new technology they need us to ask our vendors different questions.
The future of OpenStack looks bright, and with the all the software-defined data center (SDDC) features contained in the recent release of “Grizzly” they are now ready to compete toe-to-toe with heavyweights like VMware, Nutanix, Dell, and HP. Whether they can start unseating VMware products in the enterprise remains to be seen, though. Despite the immediate SDDC advantage of OpenStack, companies and technologies like that of Nicira and Virsto, both acquired by VMware, are not to be ignored.
Amazon failed because of simultaneous failure of its EBS in two Availability zones. If you were dependent on one of these (or mirrored across the two) you lost access to the filesystem from your Instances. It may be sensible to move to the use of the S3 mechanism (or some portable abstraction over it) for new applications, but if you have an existing application that expects to see a filesystem in the traditional way, Gluster can provide a distributed cloud-agnostic shared filesystem with multi-way replication (including asynchronous replication).