On Thu, Apr 26, 2012 at 5:45 PM, Carson Gaspar <car...@taltos.org> wrote: > On 4/26/12 2:17 PM, J.P. King wrote: >> I don't know SnapMirror, so I may be mistaken, but I don't see how you >> can have non-synchronous replication which can allow for seamless client >> failover (in the general case). Technically this doesn't have to be >> block based, but I've not seen anything which wasn't. Synchronous >> replication pretty much precludes DR (again, I can think of theoretical >> ways around this, but have never come across anything in practice). > > "seamless" is an over-statement, I agree. NetApp has synchronous SnapMirror > (which is only mostly synchronous...). Worst case, clients may see a > filesystem go backwards in time, but to a point-in-time consistent state.
Sure, if we assume apps make proper use of O_EXECL, O_APPEND, link(2)/unlink(2)/rename(2), sync(2), fsync(2), and fdatasync(3C) and can roll their own state back on their own. Databases typically know how to do that (e.g., SQLite3). Most apps? Doubtful. Nico -- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
