Most hard drives support S.M.A.R.T.
Problem is, most manufacturers of hard drive enclosures do not port S.M.A.R.T. support through to the computer. In fact I am not aware of any USB or FireWire drives that support it.
If you remove the internal HDD from an external USB or FireWire enclosure and connect it directly to computer's internal SATA bus (only possible on a Mac Pro really) you will likely see that the S.M.A.R.T. reporting works.
The Author of SMARTReporter, which provides SMART information, has this to say in his FAQ:
Q: Why are my FireWire/USB/SCSI based hard disk drives not seen/supported?
"Because SMARTReporter relies on the S.M.A.R.T. implementation of Mac OS X, it only supports ATA, SATA or eSATA hard disk drives, if you want S.M.A.R.T. support for your SCSI, FireWire or USB hard disk drive, send feedback to Apple."
All SCSI and some FireWire/USB hard disk drives could work if Apple implemented S.M.A.R.T. checking for SCSI and FireWire in Mac OS X (SCSI pass-through). Note that some drives could never work if their bridge controller doesn't pass support the necessary features.
That's only part of the problem. The other half of the problem is there is no standard for supporting SMART over USB/FW/SCSI. Different manufacturers use different methods.
So, along with sending feedback to Apple, send feedback to all the drive/enclosure/controller manufacturers to accept one standard.
Unfortunately I cannot speak to the NewerTech enclosure, but in principle it appears to be possible to have SMART information displayed even for external drives if the enclosure's bridge controller chip allows it.
I've used two MacPower Pleiades FW800/400/USB/eSATA enclosures for several years and I've now supplemented them with two additional inXtron enclosures. They all work as expected daisy-chained to the iMac.
The interesting thing is that the inXtron enclosures came with a CD with some software on it ("Smart AP") which is not available for download, notably a Dashboard Widget for displaying actual and maximum temperatures, total hours of operation, start/stop cycles, drive model and serial number.
This widget is complete garbage, though – it is a nauseating nightmare of extreme over-design at the expense of even basic usability:
To make matters even worse, it can only display the above information for the first external drive connected.
BUT: This Widget internally calls a command line utility which does the actual parameter retrieval, and that one can be called from the terminal as well.
So after installing the software from CD and effectively discarding the Widget, I checked out the command line utility in the Terminal and found that this utility actually reported data about ALL my enclosures, both the inXtron and the MacPower ones (there seems to be firmware compatibility across these):
(The '$' is supposed to be Terminal's bash prompt – type in only the rest of the respective line.)
$ /Applications/MacpowerAP/GetSMART 1
29 50 13 8
53 67 645 15829
52 53 90 7105
51 52 18 13
Each line reports the following for one connected enclosure:
[temp] [maxtemp] [cycles] [hours]
The drives are reported first USB, then FireWire drives, each in the order of first connection / mounting.
$ /Applications/MacpowerAP/GetSMART 2
Each drive gets two lines reported, first the drive's serial number ("***" blocking out my exact ones), then the drive model.
$ /Applications/MacpowerAP/GetSMART 3
29 50 13 8
53 67 645 15829
52 53 90 7105
51 52 18 13
This combines both of the above.
$ /Applications/MacpowerAP/GetSMART 5
This reports the mounted disk names (referring not to the volume names but to the internal Unix names as in /dev/[drive]); Numbering is in connection / mounting order, the actual sequence is as always USB drives, then FireWire drives.
$ /Applications/MacpowerAP/GetSMART 6
This reports the connection interface for each drive in the same sequence as all other commands.
$ /Applications/MacpowerAP/GetSMART 7
This might report the firmware revision or something like that.
These are the commands I know about, and they apply only to the "Smart AP" software supplied with current inXtron enclosures, but it may be possible that other brands use it as well.
I have not been able to identify information about the self-test (early(?) failure warning), but it might be contained as well in the data reported above.
As always, your mileage may vary and you should never do such experiments without FIRST making sure you've got backups of your data and that such backup is not connected during experimentation!
Maybe this can help some people getting the information they need; And maybe there are similar capabilities with other enclosures. At the very least it demonstrates that with the proper firmware in the enclosures themselves and some software on the Mac it IS possible to get at least some of the SMART information from the drive in an external FireWire- or USB-connected enclosure.
None of that is fed into the system's "official" SMART mechanism, though, so no luck using standard mechanisms or applications for it. It's strictly a command-line affair (deservedly disregarding the mishappen Widget).