Running 2009 iMac off an SSD in the optical drive only?

[patearrings]

Hi guys,

A few years ago i added an SSD drive to the optical bay of my 27" 2009 imac and made a do it yourself fusion drive.

Over the past few weeks however, the original mechanical drive (still in its original bay) has started failing. As it is such an old computer I didn't want to spend anything on it, so I just broke the core logical volume back to the original two stand alone drives and installed OSX on the SSD (which is in the optical bay).

I then found a command to stop OSX mounting the mechanical drive at all. So although it is still in the machine and plugged in, it never appears or does anything in OSX.

All was well until today, when the failing drive seems to have failed further and now has it's fan (HDD fan) spinning at around 4,000 rpm which is very loud, I tried using SMC fan control to slow it down but it just ignores it. I guess the mac is panicking that the HDD is failing/getting too hot and so is running the fans quickly?

My question is, is it possible for me to just open the iMac, disconnect the mechanical HDD's power and then run the mac as normal, or will it not like the fact there is no drive registered in the original HDD bay and only has an SSD in the optical drive bay which it thinks should be a CD drive?

Many thanks

EDIT: Is it ok to leave a failing drive in the iMac like that? I thought as it was failing and not mounted, it would just pack up and stop working and that would be that. I didn't expect it to go haywire and start telling OSX to run its fans at crazy speeds.

 

[kschendel]

I'm fairly certain that removing the HDD will not affect booting. What I'm less sure about is whether it will help your fan situation. I can never keep the year-by-year iMac HDD thermal sensor situation straight, but I think your iMac uses the HDD internal sensor with a separate readout cable from the iMac to the HDD pins. If the HDD is dead, there's nothing to read out, and the fans go nuts. If you take out the HDD entirely I'd imagine it would be the same. You may have to get one of those OWC thermal sensor kits to stop the fans. (Corrections from those who know better are welcome.)

 

[nambuccaheadsau]

Late 2009 27" iMacs and onwards need the heat sensor kit, as do the late 2009/2011 21.5" iMacs. The 2012 21.5" iMac went to the 5400rpm 2.5" notebook style hard drive tom overcome this. Wasa slow terrible answer to the problem alas..


https://eshop.macsales.com/item/OWC/DIDIMACHDD09/

 

[patearrings]

Thanks for all the help guys. I am thinking i could put a new drive it and solve it with software like mac fan control, would that work?

Also can i install any speed drive, i.e. 7200 rpm etc, or does it have to be the same speed as the one i take out?

 

[nambuccaheadsau]

In one word - perhaps. iMacs are designed to ru their own fan speeds and not be throttled by after market software.

The late 2009 27" iMacs all had a 7200rpm drive when new. Make sure it is the late 2009 model first. iMac model 10.1 for the Core 2 Duo and iMac 11.1 for the i5/i7 models.