On Wed, Apr 25, 2012 at 8:57 PM, Paul Kraus <pk1...@gmail.com> wrote: > On Wed, Apr 25, 2012 at 9:07 PM, Nico Williams <n...@cryptonector.com> wrote: >> Nothing's changed. Automounter + data migration -> rebooting clients >> (or close enough to rebooting). I.e., outage. > > Uhhh, not if you design your automounter architecture correctly > and (as Richard said) have NFS clients that are not lame to which I'll > add, automunters that actually work as advertised. I was designing > automount architectures that permitted dynamic changes with minimal to > no outages in the late 1990's. I only had a little over 100 clients > (most of which were also servers) and NIS+ (NIS ver. 3) to distribute > the indirect automount maps.
Further below you admit that you're talking about read-only data, effectively. But the world is not static. Sure, *code* is by and large static, and indeed, we segregated data by whether it was read-only (code, historical data) or not (application data, home directories). We were able to migrated *read-only* data with no outages. But for the rest? Yeah, there were always outages. Of course, we had a periodic maintenance window, with all systems rebooting within a short period, and this meant that some data migration outages were not noticeable, but they were real. > I also had to _redesign_ a number of automount strategies that > were built by people who thought that using direct maps for everything > was a good idea. That _was_ a pain in the a** due to the changes > needed at the applications to point at a different hierarchy. We used indirect maps almost exclusively. Moreover, we used hierarchical automount entries, and even -autofs mounts. We also used environment variables to control various things, such as which servers to mount what from (this was particularly useful for spreading the load on read-only static data). We used practically every feature of the automounter except for executable maps (and direct maps, when we eventually stopped using those). > It all depends on _what_ the application is doing. Something that > opens and locks a file and never releases the lock or closes the file > until the application exits will require a restart of the application > with an automounter / NFS approach. No kidding! In the real world such applications exist and get used. Nico -- _______________________________________________ zfs-discuss mailing list firstname.lastname@example.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss