On Wed, Apr 25, 2012 at 5:22 PM, Richard Elling <richard.ell...@gmail.com> wrote: > Unified namespace doesn't relieve you of 240 cross-mounts (or equivalents). > FWIW, > automounters were invented 20+ years ago to handle this in a nearly seamless > manner. > Today, we have DFS from Microsoft and NFS referrals that almost eliminate > the need > for automounter-like solutions.
I disagree vehemently. automount is a disaster because you need to synchronize changes with all those clients. That's not realistic. I've built a large automount-based namespace, replete with a distributed configuration system for setting the environment variables available to the automounter. I can tell you this: the automounter does not scale, and it certainly does not avoid the need for outages when storage migrates. With server-side, referral-based namespace construction that problem goes away, and the whole thing can be transparent w.r.t. migrations. For my money the key features a DFS must have are: - server-driven namespace construction - data migration without having to restart clients, reconfigure them, or do anything at all to them - aggressive caching - striping of file data for HPC and media environments - semantics that ultimately allow multiple processes on disparate clients to cooperate (i.e., byte range locking), but I don't think full POSIX semantics are needed (that said, I think O_EXCL is necessary, and it'd be very nice to have O_APPEND, though the latter is particularly difficult to implement and painful when there's contention if you stripe file data across multiple servers) Nico -- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
