HELP: Unable to boot

Question

OMG can sks please help. I was checking my email this morning when all of a sudden the system just froze. Nothing worked. There was a sound of the hard disk retrying to read then nothing. I rebooted but the machine just shuts down as soon as the grey screen comes on.
I have run the disk utility from the install disk and the hard disk volume is greyed out. When I run verify or repair disk it responds almost straight away with :
Invalid B-Tree node size
Volume Check failed
Error : The underlying task reported failure on exit (-9972)
1 Volume could not be repaired.
I then ran the hardware test and it found nothing wrong! I have reset Pram. Still nothing.
Has anyone got any ideas.
Many thanks
Neil

Answer 1

That sort of problem CAN be caused by a hardware issue - it sometimes results from a drive that is developing faults or bad sectors, but more often than not it's the result of a system crash when the directory structure is being written.
With the system booted to the newly formatted and reinstalled drive, check the drive with Disk Utility - under SMART status it should show 'verified', which means that the drive appears in good condition as far as the OS is able to detect (SMART is not always right, but it's a good general guide). If you get any other indication than verified, keep regular backups and be prepared for a failure. Personally in that situation and since the mini is one of the originals and thus just out of warranty, you may want to consider a bit of careful surgery to replace the original drive with a newer, faster one. It's a bit fiddly, but not too difficult to do, and there are some general guides on such service work on Mac minis to be found on the internet.