Using a public cloud provider as the back end makes the whole thing even better in several ways. First, it provides unlimited capacity, relieving the system administrators from having to track and manage free space. It also provides unlimited snapshots--one Panzura client has more than 45,000 snapshots in place. Data in the system is encrypted using AES, regardless of whether a public cloud provider is involved.
While the Alto Cloud File System is impressive, the latency involved in allowing users in different locations to access the same file system has required the company to make a few small compromises. The Panzura system locks files when applications request a record lock, which makes it unsuitable for Access databases and similar applications that are luckily fading into history anyway.
As part of the metadata, the Panzura system keeps track of where each file was modified last. In the event of a WAN failure, users get read/write access to files that were last modified locally and read-only access to files last modified in another location. While this may result in some inconvenience, it's a step up from either denying write access altogether or relying on a last update wins replication model.
While very small organizations can use Dropbox or Sugarsync to replicate files between locations, and create a backup copy while they’re at it, those services don’t provide the scale or level of service even a midsize company needs.
Panzura's Alto is another valuable tool in my storage architect's toolkit, and I can see myself using it in situations with and without a private cloud back end.
