The drive connected to the AirPort Extreme would be considered a "network" drive....while the drive connected to the iMac would be be considered an "external" drive.
If you are asking about Time Machine backups, Time Machine stores the backups differently for each type of drive location.
And...Apple does not officially support Time Machine backups to a drive that is attached to the USB port of the AirPort Extreme, so best to connect the drive directly to your iMac if you plan to use Time Machine for backups.
When a drive is plugged into the AirPort Extreme, the base station shares it over the network if it can. This makes it more easily accessible to other machines on the network(if it was plugged into a computer, that computer needs to be on and awake to share it) but also prevents it from being repaired from a computer. Drives connected to an AirPort base station need to be formatted as Mac OS Extended, FAT16, or FAT32; the filesystem capabilities of the computers on the network don't matter.
Have been using WD MyBook Studio for Mac for Time Machine and others. It has to be replaced, therefore my question.
I have a home network set up with Airport Extreme - I think. Wondering if changes to calendar/contacts on my Mac will show up on the iPad2 or iPhone4 w/o iCloud which I don't want to use?
When setting up home networks with Airport, do I need to change ITunes and others to share? I recently plugged in the iPad and asked it to sync and my contacts/calendar was duplicated. How do I prevent that in the future?
Any help, hints, comments would greatly be appreciated!