Comment 12 for bug 974275

Yes, luckily it does - so no lasting damage is/was caused. Needless to say though, until the fault was pinned down to the kernel change, there was a serious moment of panic about the possible loss of 70TiB + of data!

According to the person from the link in my first post, the problem didn't appear to exist in 2.6.32-39 but was there in 2.6.32-41; but I encountered it in 2.6.32-40. They were, however as far as I can tell, using a vanilla Debian; but assuming these kernel numbers tally-up with Ubuntu's, it appears the problem crept in somewhere in the 2.6.32-40 release.

Looking in the Debian kernel change-log, I wouldn't mind betting this would have had something to do with it:
   [ Ben Hutchings ]
   * Add longterm releases and, including:
     - md: Fix handling for devices from 2TB to 4TB in 0.90 metadata.

Unfortunately this is a very busy production machine and I have very limited time to pin point the issue further.