On Tue, 2011-01-18 at 14:51 -0500, Torrey McMahon wrote: > > On 1/18/2011 2:46 PM, Philip Brown wrote: > > My specific question is, how easily does ZFS handle*temporary* SAN > > disconnects, to one side of the mirror? > > What if the outage is only 60 seconds? > > 3 minutes? > > 10 minutes? > > an hour? > > Depends on the multipath drivers and the failure mode. For example, if > the link drops completely at the host hba connection some failover > drivers will mark the path down immediately which will propagate up the > stack faster than an intermittent connection or something father down > stream failing. > > > If we have 2x1TB drives, in a simple zfs mirror.... if one side goes > > temporarily off line, will zfs attempt to resync **1 TB** when it comes > > back? Or does it have enough intelligence to say, "oh hey I know this > > disk..and I know [these bits] are still good, so I just need to resync > > [that bit]" ? > > My understanding is yes though I can't find the reference for this. (I'm > sure someone else will find it in short order.)
ZFS's ability to handle "short-term" interruptions depend heavily on the underlying device driver. If the device driver reports the device as "dead/missing/etc" at any point, then ZFS is going to require a "zpool replace" action before it re-accepts the device. If the underlying driver simply stalls, then it's more graceful (and no user interaction is required). As far as what the resync does: ZFS does "smart" resilvering, in that it compares what the "good" side of the mirror has against what the "bad" side has, and only copies the differences over to sync them up. This is one of ZFS's great strengths, in that most other RAID systems can't do this. -- Erik Trimble Java System Support Mailstop: usca22-317 Phone: x67195 Santa Clara, CA Timezone: US/Pacific (GMT-0800) _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
