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Dead Hard Drive from Fusion Drive, how to always ignore?  

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HI guys, I heard Dave mention that he had an iMac with a split fusion drive where the spinning drive was dead but he was still using the SSD portion of the drive solo. I have 2 iMac that have the same problem so I did the same thing and separated the Fusion drive and installed the system on the SSD. BUT, I get a warning after some time being logged in that a drive couldn't be mounted would I like to initialize, ignore or eject. I click ignore, but I have to do this every time the Mac is restarted. How do you deal with this Dave? Also, I had a Sierra installer but can't get High Sierra anywhere:-( I'll have to upgrade to Mojave, which I'm not too thrilled to do on this machine (iMac late 2012).

ok, found it

https://github.com/aburgh/Disk-Arbitrator

Normally this tool is used to prevent a disk from mounting, being written to, useful when running disk forensics on a dying disk. It will do the job for you.

On the said GitHub page, scroll down to the downloads link where you will find a releases link.

Hope it helps.

Hey Alex, checked your Disk Arbitrator, unfortunately, since there is no Volume created on this disk, it can't block it. I guess this is good if you have a working drive. Still have to check the other option with the command line. I did find a command line but everything I try happens AFTER whatever my mac is doing to try to spin it. I guess I'll wait for Dave to find a way to deal with it 😉 .

Hey Alex, checked your Disk Arbitrator, unfortunately, since there is no Volume created on this disk, it can't block it. I guess this is good if you have a working drive. Still have to check the other option with the command line. I did find a command line but everything I try happens AFTER whatever my mac is doing to try to spin it. I guess I'll wait for Dave to find a way to deal with it 😉 .

In the terminal type the following:

diskutil list

Does the output suggest that the uninitialized drive is there? You should see something, regardless if the drive is mounted or not. If you don't the drive may be already intermittent due to the nature of the failure.

Actually this utility should work because it is meant for keeping disks that are failing from mounting, being written to or interacted with so that a forensics tool can do it's repair/recovery without interruption but if you say this utility doesn't meet the goal you are trying to reach it leads me to believe that the drive is at some stage of failure that it doesn't even show up in a "diskutil list" from the command line.

You might want to try "diskutil eject /dev/disk#" and the number of the drive and then block it from trying to mount again using the utility I referred you to.

Unfortunately, I don't think MacOS refers to drives by a UUID which could allow very specific targeting.

Another approach perhaps is as follows but it would rely on it showing up via a "diskutil list". If it is always the same /dev/disk# between restarts it should be safe to assume that it shows up to the OS in a repeatable sequence. If this is the case, you could attach the "diskutil eject /dev/disk#" to an AppleScript and assign it as a startup item. This could potentially always eject the drive but the beauty of that app is that it will force that device from ever even wanting to mount period.

Anyway Disk Arbitrator's name is pretty keen, borrowed right from the framework, Disk Arbitration: https://developer.apple.com/library/archive/documentation/DriversKernelHardware/Conceptual/DiskArbitrationProgGuide/Introduction/Introduction.html

@Alex I can see the disk when using the diskutil list command, disk2 in my case. When I launch the disk arbritator, I can see the drive, but when I get info on it, it says it cannot be mounted, or unmounted. So I don't know how that would work. Here's what I see in terminal and Disk arbritator.

disk info

@Alex, I've tried this command "hdiutil eject disk2" in a Keyboard maestro macro that execute at login. I also tried it as a Launchd with a plist file and it still did't work. 

If the disk that mounts, that you don't want to mount always has the same dev/disk# and you want it to unmount immediately maybe this will work for you.

Launch automator and choose an Application Document

enter this but replace # with the actual disk #, use disktutil list to find out what it is:

do shell script ("diskutil eject /dev/disk#")

Save it as an app somewhere and then from the Users & Groups System Preferences, have it launch on startup by adding the app to the Login Items.

Not sure if this helps or not.

Screen Shot 2018 10 10 at 10.27.30 PM.min

 

@Alex, so I tried your script and put it in an Automator app that I put in the account login. Same result, although it might work normally, I had restarted the mac last night but not logged in right away (I'm connecting remotely). When I check this morning, right after logging in, I had the message. Probably because what ever check the OS is doing was done before I logged in. Anyway, I've spent to much time already for something like this. Thanks for your help!

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If you have ever installed High Sierra on any machine you've owned, you still should find it available for download in your Mac App Store Purchased items. 

Regarding your damaged drive, if you're not going to have the spinning drive replaced or removed, I vaguely recall or suspect there's a command line instruction to label the physical Disk ID to be ignored or disabled (?) I'm not sure on that.

 
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First, the High Sierra Installer is still available at the Mac App Store... we always save these links. 😉

Second, @jefflambert670, you're absolutely right about my scenario. That's on the iMac in the Studio where we record. And, yep, I have to hit "Eject" after booting the machine. At some point I just need to pop that drive out of there. 😉

Thanks for the link to the installer. Thing is, I did install High Sierra on MY mac, but this was a company computer and I did't want it to be linked to my Apple ID, I thought I had downloaded it with the company's Apple ID but no, so Anyway it's running Mojave now. 

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