That's a sizable operation and difficult to visualize. I'm guessing their failure points reduce potential damage to minimal levels. At AltDrive, we use ZFS RaidZ2 with a number of hot spares. Six drives would have to fail consecutively on a given machine before any data loss... we replace them as they occur. And we have inter-H/W duplication. ZFS is self healing and makes management easy. Additionally we periodically compare the integrity of the user's AES-256 CTR encrypted data against the database records and make corrections if necessary. From our customer's and white label provider's view, it just works. http://altdrive.com