I have been backing up my 3 Macs (MacBook Air, MacBook Pro and iMac) to an Apple Time Capsule - without issue. I recently experimented with backing up my MacBook Pro (mid 2010) to the MyBook Live. The backup is successful - although it runs slightly slower than the backup to the Time Capsule - but what concerns me is that the backup does not always start when expected - when backing up to the MyBook live.
When backing up to the Time Capsule - all of my Macs will begin the backup within 30 to 60 seconds after waking from sleep and then every hour afterward. When I back up to the MyBook Live - the backup never starts within 30 to 60 secons of waking from sleep - rather it will start about 20 to 40 minutes after the MacBook Pro wakes. In many cases - the MacBook pro has already gone back to sleep before the backup starts.
In a couple of other circumstances - the Time Machine backup will not backup (even an hour later) at the stated time - and then waits yet another hour before beginning the backup.
Why is Time Machine behaving differently when it backs up to the MyBook Live - vs - the Time Capsule? In the MyBook Live scenario - there is a high likliness of many backups being skipped because the backup does not start upon wake from sleep.
Has anybody noticed this behavior. I have only tested it on the MacBook Pro.