For several days now, I’ve been trying to get my problem Seagate 3T disk (single partition) to fail again while running Mavericks. I began by using a USB3 Interface/base (which only works at USB2 speeds on my MBP). I would eject, un-attach and re-attach the single partition using the Finder or unmount and re-mount it using Disk Utility. When it didn't fail, I started copying GBs of data to it then ejecting or un-mounting and re-mounting. It worked fine.
So I switched to a FW800 interface/base, mounted it, copied 40ish GB of data and un-mounted it with Disk Utility and immediately asked DU to re-mount it. Bingo.... it failed to mount. And, as before, Mavericks Disk Utility could not verify or repair the volume. The repair fails at
“Checking the file system
Volume repair complete.
Updating boot support partitions for the volume as required.
Error: …."
I shut down and rebooted into Snow Leopard (10.6.8) with the drive still attached. The drive did not mount and SL’s Disk Utility could not verify or repair the volume (same story as DU in Mavericks). So I ejected the drive using DU and switched back to the USB3 interface/base. When I reattached the drive it mounted and verified!
I ejected the volume and restarted in Mavericks with the drive still attached. The drive mounted and verified!
So either this brand new FW800 interface/base is bad or Mavericks does not always handle this FW800 interface correctly, leaving the volume slightly damaged after un-mounting it. In either case, I’ll be using the USB interface/bases until this issue is resolved.
— GetRealBro
BTW the unmount/mount problems I have reported are at the partition/volume level, not the whole drive. While this drive has only one 3T partition/volume, the other problem 3T drive had two partitions. And only one of them had mounting issues.