During a recent investigation, Jones Dykstra and Associates was asked to acquire information from a Western Digital (WD) Passport 2 external drive with a USB Mini-B interface.  When we plugged this hard drive into our Tableau T8 USB forensic bridge in order to write-block it, the device was not recognized.  Since all of the WD Passport drives we tried previously had worked with this write-blocker, the problem was unexpected.  We made sure that our firmware was up to date and swapped out different USB cables and T8s, but continued to experience difficulties.

To sort out the issue, we called Tableau tech support.  Tableau informed us that certain drives do not receive enough power from the T8, and that a powered USB hub was required for these drives to work.  We connected the Passport to a Belkin USB 2.0 4-port powered hub.  The drive remained unrecognized.

Tech support could not figure it out; they mirrored our setup, but had no problems.  After a few minutes of comparison, we figured out that the only difference was that Tableau tech support was using a USB 1.1 powered hub, but we were using a newer USB 2.0 powered hub.  When they switched over to a USB 2.0 hub to match our configuration, they immediately experienced the same problem we'd been having, and confirmed that this was a new compatibility issue with USB 2.0 hubs.  Our support request was forward this to their engineering group, but we were given no timeframe for an expected fix; Tableau's only workaround was to use USB 1.1 instead of 2.0.

At this point, there are a few questions some might ask:

• Why not just remove the casing from the external drive and use the hard drive's interface instead of the enclosure's USB? Like many other currently-produced externals, the WD Passport 2 is basically one piece of sealed hardware; these drives are not merely easily-removable laptop drives inside enclosures.
• Well, then why not just use USB 1.1 instead, as Tableau suggested? USB 2.0 can transfer data at 480Mbps, which is forty times faster than USB 1.1. For standard, low-volume transfers, USB 1.1 might be acceptable, but when duplicating hundreds of gigabytes of data, using 1.1 could delay work on a project by days.

Since Tableau could not provide us with a workaround other than to use a version of USB that is unacceptably slow, we sat down and came up with a workaround that utilized USB 2.0 transfer speeds and is even cheaper than buying a 1.1 hub: we swapped out the powered hub with a special USB cable known as a "Y cable."

A USB Y cable (shown here) is made up of two type-A male USB connectors and one type-A female USB connector.  The Y cable's male connectors include one normal USB connector (which transfers both data and power), and one that is dedicated to providing the device with power.  We could therefore plug the WD Passport's USB cord into the female end of the Y splitter, then connect the standard male USB into the T8, and connect the male dedicated power connector to any available USB port on our computer.  We tested this setup as if the bridge was being used as intended by Tableau, and the WD Passport was both recognized and write-protected.

We contacted Tableau with this solution on October 29, 2008, and they acknowledged our workaround as a viable solution to this problem.  If you are experiencing the same difficulties write-protecting your external drives, USB Y cables for our workaround can be purchased on Amazon.  Until the USB 2.0 compatibility issue is resolved, this is the cheapest and most efficient workaround we know of.

We'll keep you apprised of any new developments.