How long to 'build a local snapshot' ?

I've got one ReadyNAS pro unit that seems to take forever to get through its, "Building Local Snapshot" phase. It has to chew through 1.2 TB of data, but how long should this take?? Since there is no progress bar or other info, I don't know if its almost done, or should I just stop and start it again, or reboot the NAS?

I just upgraded to 8.0.7.0, from 8.0.5 and was having the same issue. Any guidence here would be very helpful. I've got two other identical units with the same OLC version that are humming like tops.