I prefer to architect to use redis in an ephemeral way. Redis isn't exactly safe in the same way postgresql was up until very recently on newer linux. The semantics of fsync on Linux have been esoteric and poorly understood in the error cases. I would try to cause fsync to fail in another process, while memcached is shutting down and immediately recover. I wonder if the authors checked this scenario. Redis kindof does the right thing and will eventually put the right thing on disk but why do it?
Note that that only was an issue in cases the storage system itself was failing (i.e. IO errors were generated). In contrast to protection against power failures etc, which was/is working correctly.
