Isolating iMac HDD Issue



Observation - iMac suffers hard crashes (does not accept input from mouse etc; sometimes repeats the last sound byte repeatedly; needs to have power button held in for 10 seconds to turn the machine off) at random times - sometimes when it is not directly being used ie in sleep/idle.

Theory - HDD inside Early 2009 iMac 24" is flaky, resulting in random system failures.

Proposed Diagnosis Method - Boot from external USB drive and test iMac to see if it crashes.

Method Note #1 - Use clone of existing internal drive to rule out software issues.

Method Note #2 - Use fresh instal if #1 still results in failures.

Is that method sound? Or will the iMac still “use / access” the internal drive, even if I do not tell the machine to access its data? Can the drive still cause issues simply because it will automatically mount?

Basically I am looking for a diagnosis without having to replace the hard drive… I thought this may save me some time / messing around inside the machine…




It’s certainly possible.

I came across one machine that was intermittently crashing. It was previously in at Apple for a Logic Board and Power Supply replacement. I suspected the Fusion Drive SSD - the kernel panics were related to IOStorageFamily - and decided to back up the data before testing further.

When that iMac was connected to another machine, the other computer would intermittently crash with the same IOStorageFamily crashes. It didn’t matter what the connection interface was, FireWire or Thunderbolt produced the same crashes on more than one machine. It was the process of mounting the drive and accessing the data on it that caused the crashes, even though the machine wasn’t booted or reading any system data from it.

So it’s certainly possible that it could continue to crash, and that crash could be attributed to the internal drive, even if booted from another volume.

That said, it’s extremely uncommon. I would perform the test anyway, because it’s a good first step. The methods are solid, if not a bit time consuming, because you’re attempting to isolate both the hardware and software. Good move.


Thanks for the reply, @iMic. I’ll try that option then to try confirm if it’s the HDD. Hopefully that’s all it is, and I’ll sell it on to help pay for a SSD for my MacPro5,1.


If it happens even whilst your computer is asleep, then your theory would only apply if: 1. You have scheduled some activity that causes the mac to wake up and access the internal disk, or
2. You have set the mac to wake on a network request, and then it accesses the hard disk.

If neither of the above occur, then it may well not be related to your internal disk.


Hi @snarl :slight_smile: Sorry - shouldn’t have said sleep - really just meant the monitor going to sleep. The iMac (was) set up as a Plex Server, so was “always on”. Really just meant that it could freeze even when it was not being used at all.