> I must not be being clear. Tell me if this scenario is possible: > > * Client A writes to file foo many times and it is journaled to object set 1. > * Client B writes to file bar many times and it starts journaling to > object set 1, but hits the end and moves on to object set 2. > * Client A hits a synchronization point in its higher-level logic. > * Client A fsyncs file foo to object set 1 and then > * Client B hits the synchronization point, fsyncs file bar to object > set 2, and sends data back to Client A. > * Client A fsyncs the receipt of its data stream to object set 1, and > only then gets sent on to object set 2. > * The journal copier runs and migrates object set 1 to a remote data > center, then the data center explodes. > * In the remote data center they fail over and client A thinks it has > reached a synchronization point and gotten an acknowledgement that > client B has never heard of. > > Does that being a problem make sense? I don't think handling it is > overly complicated and it's kind of important. > -Greg
Seems this case is solved if you delay the completion of client B's flush (fsync) until the "active set updated" notification is successfully delivered. In that case, client A would know that it needs to re-read the active set collection and thus needs to now write to object set 2. Thoughts? -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
