We've pulled the power during a write on ZFS and we didn't have any sort of corruption. The write just wouldn't occur on the second disk until the power comes back.
The snapshots are of the entire disks. We have servers in SharkTech and other places that serve as load-balancers for us. In the situation of a disaster at one of our DC's, we could use an existing server in a different location. Do a full rsync of the data and have the users online in an hour.
DR is incredibly expensive and as most companies, our most critical infrastructure (DNS/Company support/etc) has an immediate failover configuration with backups pushed to up to 4 systems geographically. There is always a possibility of slight disruption due to propagation. Customer data is also extremely important and we make every effort to have available backups. Depending on the server and the user's plan, really depends on how fast they will be back online.
We do some IRC hosting for Sun Microsystems and other companies. Services such as those have an immediate failover plan. Others, in a disaster, could suffer an up to 6 hour outage. Of course, this would be a situation where there was a real disaster such as a fire, flood, earthquake, etc.
If anyone has any questions or would like some help on DR planning, I'd be happy to assist.
R1Soft is for sure a life saver. Unfortunately I am not sure if it was just lack of knowledge on how to operate it or what, however we had it fail on a 250GB server restore at 65% and then have to start from the beginning. The process seemed to take forever! At the time, we was with a company who provided managed R1Soft under their own "brand", and I wont drop their name in here because they are always running adds here and have a very favorable reputation here, however the restore process of the ~250 took almost 16 hours for the server with them... . We received a rather nice credit and they acknowledged the process was not handled correctly by their management.
That being said, no data was lost so that's a plus. R1Soft IS a life saver. I do think you should if your budget allows, have some sort of an additional fail over besides R1Soft in case it fails you