TechTool Pro 4.1.2: Potentially erroneous disk error messages (misdiagnoses); cause of the problem

Several readers are reporting potentially erroneous messages indicating diagnostic issues with various drives from TechTool Pro 4.1.2. The same error messages were not reported with TechTool Pro 4.1.1.

Most users report that parts of the Read/Write drive test fail with error code -1421 when run on startup volumes. However, the failures do not occur with every scan. In other words, it appears that TechTool Pro is providing inconsistent results with repeated scans, indicating that it may be picking up drive errors that do not exist (i.e. misdiagnosed drive errors).

MacFixIt reader Bill Weylock writes:

"Immediately after upgrading from 4.1.1, I ran TechTool 4.1.2 on my system and all of my drives and volumes.

"It reported a 'linear write' failure on a brand new (less than 1 week out of the box) LaCie 500gb d2 drive connected with FW800. Re-running test gave same result.

"After running Disk Utility (passed) and after preparing to zero over-write the drive, I decided to run TT one more time. No linear write error. Surface scan passed. If I were alone, that would simply be a boring 'one of those things'story. Going to the Micromat forum page, however, I found several people with the same or very similar problems: drive functioning perfectly, good reports from TT 4.1.1 (not true for me on that drive since it was new), and an immediate read/write error from 4.1.2."

It now appears that this problem is caused because the Read Write test tries to create a temp file on the drive to test it, and version 4.1.2 of TechTool Pro uses uses a unicode name for the file. A Micromat (developer of TechTool Pro) technical support representative states:

"Some older file systems components have a problem with this and return the error. You can disregard the error--it is a misdiagnosis. The Read Write tests are low level tests. If the drive is functioning, then the drive's Read Write mechanism would not be bad. It is only in the case of a massive drive hardware failure that this might give some extra information about the type of failure."

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