We have a machine which has been using 1tb of storage with a 1tb backup. we have added a 2tb drive. is it possible to add a 2tb backup disk to the mix and have time machine manage backing up the 1 to 1 and 2 to 2? Or is it necessary to get a 3tb drive for the full backup?
Any input on this would be helpful?
See my post:
https://discussions.apple.com/thread/4571474
It might help (depending on what the responses contain).
You can't pool drives within TM to make a single larger volume. You can combine drives to form a striped RAID in Disk Utility, but the capacity of the RAID volume will be twice that of the smaller drive, not the sum of the two. I wouldn't recommend that for backup as it's not reliable enough.
As of Mountain Lion what I read says that TimeMachine can have multiple disks to back up to and will write backup data to whatever drives you add to your "pool".
This does not seem to work if any drive is smaller than the dataset you are backing up. That is, apparently TimeMachine wants to put all the data from one machine in one place on one drive and if the drive it is looking at is too small it bails out with an error and tells you to reduce the data set size or get a bigger disk?
Time machine - multiple disks and multiple backup disks
