It is quite possible that software and firmware updates in Lion are preventing you from "seeing" the drive as a Time Machine destination.
Apple has not, and does not officially support this type of method for Time Machine backups.
Folks try it anyway. A few users seem to be able to make this work, some have some limited success and some have no success.
Having tried this myself as an experiment at least a dozen times over the past few years as new operating systems and firmware updates appear, I remain strongly in the "no success" category.
You might try a powered USB hub to see if that will allow the disk to be "seen". But, even if it does, the odds are stacked against you....so it might be a good idea to have a secondary backup plan in place.
If you think about it.....
Apple has control over the hard drive and interface software / hardware when backups are made on a Time Capsule...so everything is optimized for reliable backups.
Apple has no control over the hard drive or interface when you connect another hard drive to the USB port on the AirPort Extreme using Time Machine backups. It is a matter of chance that things will or might work.
It really makes no difference if you backup using a direct Ethernet connection or wireless....except Ethernet will almost always be much faster.
Under Airport Utility, under "disks," I am able to "see" the disk connected to the base station. What is the puprose of the disks tab under this utility, if it allows for no connectivity to the attached disk. It seems superfluous, a vestige of something that once worked, but no longer does.
Thanks for your indulgence of this line of questioning. I've given up on trying to see the disk under time machine.
What is the puprose of the disks tab under this utility, if it allows for no connectivity to the attached disk.
It does for me if I connect a drive to the USB port on the AirPort Extreme, whether I want to try Time Machine or not.
I can move "normal" data from a Mac over to the drive connected at the USB port of the Extreme with no problems.
I can also setup Time Machine backups to the same drive....but it is a matter of time as to when they will become corrupted. Sometimes happens of the first backup. Other times I can go up to a few weeks before backups become corrupted.
How exactly, are you trying to access the drive that is attached to the USB port on the AirPort Extreme from your Mac?
Well, I'd like to be able to access it via Time Machine. But the disk that is visible under the disks tab does nothing accept appear under that tab for me. It doesn't mount on the desktop, if double clicked. It just shows up there, for me. I'm not sure what I'm not doing. What should one be able to do with that visible disk? It seems to me, access it, and mount it onto the desktop. If it doesn't do that, than it's not functional.
I can't connect to server either under finder. The AC rep also tried me having to do that, although he didn't exactly explain why.
Open Macintosh HD and look for the AirPort Extreme icon under the SHARED heading on the left side of the window
Click the AirPort Extreme and a folder representing your hard drive will appear to the right
You may need to click Connect As (in the upper right corner of the window) the first time that you do this and enter the device password for the AirPort Extreme or if you assigned a different password to the hard drive, then enter that password
Double click the folder with the name of the drive to mount the hard drive on the desktop
If the drive does not appear, then click anywhere so that the Finder menus appear at the top of the screen. Click Finder, then Preferences. Click the General tab. Under the heading of "Show these items on the desktop", make sure that all boxes are checked.
As I mentioned previously, you may need to use a powered USB hub with the AirPort Extreme. The USB port on your Mac is high power. The USB port on the Extreme is not. I almost always have to use a powered USB hub with any hard drive that is attached to the AirPort Extreme (or Time Capsule).
its not officially supported, but this is what i do:
use Finder's "Connect to server" and browse your network for the APE, then into the USB volume. next right-click the USB drive's name at the bottom of the window and select "Open enclosing folder" -- this shows you the drive as an icon, along w/ any other physical drives you drive. drag the drive on the left-hand dock, where it will register under "Devices".
now when you visit the TM prefs it will show up as an available drive to use. I've tested it w/ restoring deleted files or over-written files, which is about all i expect it to work for, but have not tried a full restore.
The reason backing-up to a USB drive connected to an Airport Extreme is not supported is, it's generally unreliable. Yes, it may work for some number of days, weeks, or even months, but in most cases the backups will turn up corrupted, sooner or later, often beyond repair.
As long as you either have other, more reliable backups, or don't mind risking the loss of your data, the convenience may outweigh the risks.
But it's not a good idea to recommend it without clearly specifying the very real possibility that the backups may turn out to be useless just when they're needed the most.
Yes, as posted, it does work in some circumstances, for some period of time.
There are also many, many posts in these forums by folks who backed-up that way for a time, sometimes quite a long time; then there was a problem with their Macs and they needed to do a full restore, but the backups were corrupted beyond repair, and they lost everything.
My point is, it's irresponsible to provide a workaround without including some mention of the risks.