We discovered a bug in the MacPro/MacOS (both Nehalem and Westmere) using OS10.6.8. If you put a firewire 800 drive on each of the rear ports, after an indeterminate period of time ranging from 20 minutes to a couple of hours the MacOS and any apps using those drives loses the ability to access the drives. The files are “unavailable” and the folders not cached do not show contents when you navigate to them. They still show in the Finder and Disk Utility shows them as mounted. Disk Repair does not bring them back and you must do a Force Eject to unmount them. Remounting them brings them back until they become nonfunctional again.
This happens in Nuendo, in ProTools, and eventually using the Finder if you’re accessing the drives. Something in the OS loses track of them. Daisy-chaining them on a single port works fine, we recorded 128 tracks to two drives for several weeks after finding this.
Specifically not tested -
OS10.7, although a colleague reports he “had an issue with PT10 under OS10.7.3 and multiple firewire drives”, he daisy-chained them and was fine after that. Correlation is not causation but could be the same issue.
I’m suspecting this may be the cause of a problem we had on all our MacPros when we updated to v5.5.2 and did not consider dual ports as a variable. All systems at the time had two firewire drives, one on each port. Variables.
Hope this helps someone.