+ // blobSignatureTTL, Delete must not delete the data.
+ //
+ // If a Delete operation overlaps with any Touch or Put
+ // operations on the same locator, the implementation must
+ // ensure one of the following outcomes:
+ //
+ // - Touch and Put return a non-nil error, or
+ // - Delete does not delete the block, or
+ // - Both of the above.
+ //
+ // If it is possible for the storage device to be accessed by
+ // a different process or host, the synchronization mechanism
+ // should also guard against races with other processes and
+ // hosts. If such a mechanism is not available, there must be
+ // a mechanism for detecting unsafe configurations, alerting
+ // the operator, and aborting or falling back to a read-only
+ // state. In other words, running multiple keepstore processes
+ // with the same underlying storage device must either work
+ // reliably or fail outright.