Comment by masklinn

> So, in the event of a failure in the underlying hardware, the data may have been transferred, but subsequently an error has occurred. I don't see how the sentence obliges the implementation to transfer multiple times. I'm not an expert though.

That is actually an issue with disks which have a small memory buffer before actually writing to persistent storage: not only will they acknowledge success as soon as the data's in their buffer (losing information in case of error in the underlying storage write) they may not properly handle a power loss of some sort, ack'ing the write to the buffer then losing it before it has the time to hit storage.