Ross Smith wrote: > Triple mirroring you say? That'd be me then :D > > The reason I really want to get ZFS timeouts sorted is that our long > term goal is to mirror that over two servers too, giving us a pool > mirrored across two servers, each of which is actually a zfs iscsi > volume hosted on triply mirrored disks. > > Oh, and we'll have two sets of online off-site backups running > raid-z2, plus a set of off-line backups too. > > All in all I'm pretty happy with the integrity of the data, wouldn't > want to use anything other than ZFS for that now. I'd just like to > get the availability working a bit better, without having to go back > to buying raid controllers. We have big plans for that too; once we > get the iSCSI / iSER timeout issue sorted our long term availability > goals are to have the setup I mentioned above hosted out from a pair > of clustered Solaris NFS / CIFS servers. > > Failover time on the cluster is currently in the order of 5-10 > seconds, if I can get the detection of a bad iSCSI link down under 2 > seconds we'll essentially have a worst case scenario of < 15 seconds > downtime.
I don't think this is possible for a stable system. 2 second failure detection for IP networks is troublesome for a wide variety of reasons. Even with Solaris Clusters, we can show consistent failover times for NFS services on the order of a minute (2-3 client retry intervals, including backoff). But getting to consistent sub-minute failover for a service like NFS might be a bridge too far, given the current technology and the amount of customization required to "make it work"^TM. > Downtime that low means it's effectively transparent for our users as > all of our applications can cope with that seamlessly, and I'd really > love to be able to do that this calendar year. I think most people (traders are a notable exception) and applications can deal with larger recovery times, as long as human-intervention is not required. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
