-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Jeffrey Hutzelman wrote: | --On Monday, April 07, 2008 12:30:06 PM -0400 Matt Benjamin | | You'd think that, but the problem is that you generally can't. Cache | consistency demands that when a file's contents are changed, you break | callbacks to any online clients before the RPC that made the change | returns. That means you can't queue them up to combine later. |
That avoids saying what the cache consistency guarantee in AFS is, though it's not in doubt--even if I do misunderstand some aspect of it, or the whole thing. :) In AFS today, if clients A and B have made changes in a file, and have not stored, there is a race to store. I do not think the race is eliminated by the fact that the call back break from the first-client-to-store (say, A) is executed before the clients store completes. This cannot undo the changes made on B before it received the call back break (that B must store or discard). (I assume we don't send a call back break to A in that case, but I haven't looked.) In the case of lock-coordinated access to regions of a file, we expect that B's client's cannot write to a range R(A), until A's lock is released. So there is no race to store. If we were queuing changes to combine later, seems like it would suffice that queued changes to R(A), if any), be flushed when A's lock is released. Before that, it seems they could be best-effort--and are anyway. Matt - -- Matt Benjamin The Linux Box 206 South Fifth Ave. Suite 150 Ann Arbor, MI 48104 http://linuxbox.com tel. 734-761-4689 fax. 734-769-8938 cel. 734-216-5309 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFH+mPjJiSUUSaRdSURCGNnAJ97QYzkEcloBAR8Z+086N+ZeKYUgACfUhKi IBp/gPhYozCnNI6QpMl7R7E= =e8TT -----END PGP SIGNATURE----- _______________________________________________ AFS3-standardization mailing list [email protected] http://michigan-openafs-lists.central.org/mailman/listinfo/afs3-standardization
