Six Lessons Learned from Dealing with an iMac's Dead SSD

I completely agree with @doughogg about the desirability of having an iMac which doesn’t easily allow you access to change a failing SSD (or other component).

I was faced with this decision recently as my existing iMac 5K aged and increasingly looked set to cook its internals (not to mention strained to run things with its ancient graphics chip). I thought about the iMac Pro since it at least has better cooling and might avoid cooking the internals. Or I could chance it with a newer iMac, since they seem to be more thermally efficient - but I’d still be stuck with non-upgradeable components.

In the end I bit the bullet and splashed out for a Mac Pro. I can’t see Apple producing a cheaper Mac Pro for a while (if ever). The cost is a lot more than I’d ideally spend - but at least I now have a machine that should last for a long time and is reasonably easy to fix/upgrade (at least until Apple switch to ARM chips). :roll_eyes:


Great article @ace! It’s given me a lot to consider. My late-2012 27 inch iMac is even further outside the replacement window that @Jim_Carr recommends. I replaced the failing original 1TB spinner hard drive with a 1TB SSD drive in 2016, and it gave a huge performance boost to the machine. I found that peeling off the monitor and reattaching it worked fine for me, but I am a meticulous and patient worker in that regard.

For compatibility reasons I’m still running under High Sierra. It is still receiving security updates, which surprises me given Apple’s earlier history with the every-year OS rollouts.

The stuff I have to think about: For the last six weeks I have pressed this iMac into heavy-duty video production to support recorded and live online services for my work. That means in my case about 30 minutes of polished video segments using Final Cut Pro and Motion, mixing an 8-voice choir submitting separate audio files using Garageband (because I’m not ready to add Logic to my toolkit yet), and producing many stills with Photoshop and the Affinity suite.

The first week of work flooded the remaining space on the internal SSD, so I asked OWC for a recommendation and added a Thunderbay 4 Mini RAID. It works acceptably well for storage and rendering all those FCP files connected via Thunderbolt, and I anticipate bringing it along to a machine that can run it at Thunderbolt 2 speeds.

So, I’m pushing a nearly-vintage iMac as hard and fast and full as it can go, meantime recalling the previous 2008 iMac that suddenly went black one day and could not be revived, even by techs at my local Apple Store. They handed that one back to me, and had pulled the hard drive in case I wanted to try recovering it. (That was a no-go as well.)

My concerns are:

  • I had to purchase Disk Warrior due to an early directory problem with the RAID. That was sorted out fine, but DW apparently won’t work with my internal SSD on High Sierra, and still doesn’t appear to work at all with APFS-formatted drives.
  • Replacing the iMac will let me update to the latest versions of Apple software like FCPro, but will leave behind all the 32-bit apps that Apple has now locked out.
  • I won’t have the time to troubleshoot anything at all if this machine winks out. I’m on an inflexible production schedule and I’ll have to invent a new workflow in the middle of a cycle.

So, with all of that in front of me, I’m STILL very appreciative of the article. I’ve been thinking of my iMac as an iron warrior, but your experience and the helpful way you’ve related it have brought me to realize I need some backup plans in this environment.

A tip: Split Fusion Drive to get two drives and hopefully the SSD part or both is still alive.

Caution: You will lose all your files and will have to restore the system. The SSD disk is small compared to the spinning disk and the spinn disk is slow.

I would like to share this with you regarding Fusion Drive. My experience is from doing this with 8 different macminis, that we had at work and now functions as home computers for our Graphic Designers. The reason I did it was an experiment because they all were unstable back in 2015 and we replaced them with macminis with standard SSD’s. All split drives are still going strong today.

Boot via Internet Recovery Mode.
Get into the terminal
diskutil coreStorage list
Copy Logical volume group id at top it’s a long hyphenated string of numbers and letters.
diskutil coreStorage delete
Quit terminal
Start Disk Utility.
Now you see two disks in Disk Utility. If Disk Utility asks to restore Fusion you can try that, but if things do not work, do the split again. You can now use Disk Utility to check both disks. Use “Get Info” on the disks to see which is SSD (Solid state : Yes) and what the SMART Status is (SMART status : Verified). Do repair on both and restore the system.

My 15" mid 2012 MBP (OS 10.14.6) has suffered very rare but catastrophic failures of the built in 500GB SSD for the at least 4 years. Nobody has been able to identify the cause, only happens about once/year. My solution (apart from multiple clones and Time Machine ) is a very inexpensive 250 GB SSD in a USB3 case: 2 partitions with Sierra in one and Mojave in the other. It is NOT a long term working solution, a bit sluggish on the start up. But very cheap <$50., easy to upgrade, and so far I just re-format the built in SSD, use my clone to re-build + update w TimeMachine, about a 3 hour turn around and I’m good 'till the next crash (I actually suspect a doggy connection someplace on the MBP bus, but it is not replicable, so I cannot be certain). Yes, a new MBP would be nice, an external SSD may solve the problem -or not, but having a reliable alternative start-up disk has gotten me out of a lot of sinkholes and I’d recommend it for anyone whose work depends on a computer. (Earlier I used a 64GB micro chip; that works too, if you do not want to be able to fall back on the previous OS). Just don’t forget to run software update every month or so over-night on your spare start-ups.

Interesting possibility! In this case, I don’t think that’s happening since it appears as Unknown in the SATA section of System Information.

Thanks! I figured that these techniques weren’t necessarily things people did every day, so it was worth a few more words to explain how to do them as well.

Fingers crossed it doesn’t come to that, since Apple doesn’t seem to be doing too well with repairing Mac Pros.

Apple has a policy of supporting the two previous macOS versions, so that would be Mojave and High Sierra. Once the next version of macOS comes out, however, High Sierra will be kicked off the back of the train. Another thing to consider when pondering an upgrade.

In thinking about your situation, I would recommend buying a new iMac right away. Doing that gives you the opportunity to transition to it gently while the old iMac continues to work as you’ve come to expect. Also, it will be loads faster for the exact sort of things you’re doing. In fact, I’d buy the new iMac, start using it immediately, and only rely on the old iMac for parts of the workflow that can’t be transitioned immediately. Those can then be moved over as you have time.

DiskWarrior has long been a great app, but I have to say, I haven’t used it in decades. Mac drives, particularly SSDs in my experience, don’t seem to suffer directory problems nearly as often as they used to. If Disk Utility can’t fix something, I’d prefer to reformat and restore rather than trust that any third-party could do better than Apple’s own engineers, particularly given that APFS documentation is still sparse, as I understand it. I would never recommend holding up an upgrade for DiskWarrior. Just make sure you have great backups.

Interestingly, the old 2014 iMac I got back from @jcenters had a Fusion Drive, and it looks like he split it. The SSD is largely non-functional (the Finder asks to initialize it, but it always fails in Disk Utility) and while the hard drive seems to work, I strongly suspect that the machine’s flakiness is due to having the dead SSD in there.

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In another thread, @Simon just shed some light on one of my mysteries—why my Mojave installer claimed it was corrupted.

Since my external SSD was empty, I didn’t even think to copy the Mojave installer to the SSD and install from there. Why would the installer care where it was being launched from?

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Just one word of warning from someone who has lived with a dead internal drive (HDD) for years in his iMac 27" late 2012. After the drive failed, it was still mounting, which caused problems at times even when I managed to erase it. I edited fstab to unmount the drive automatically:

  1. identify the drive using (in Terminal) diskutil list (mine was /dev/disk1s2)
  2. find the UUID using diskutil info /dev/disk1s2 | grepUUID (mine was 158A8B51-0C4F-490B-9432-FB1767AAAC07)
  3. edit /etc/fstab using an editor compatible with the Terminal, adding the line:
    UUID=158A8B51-0C4F-490B-9432-FB1767AAAC07 none hfs rw,noauto 0 0 (substitute your own UUID)

This unmounts the drive automatically but you can expect trouble at times, particularly when updating your operating system on your external drive (mine is an SSD connected by USB 3.0). It can take an eternity to complete, and I have at times had to abort the process and retry, so far successfully. I really ought to open the machine up and remove the offending HDD, replacing it with the SSD - I have the tools and the replacement adhesive strips, but have never bitten the bullet.

Yes, maybe it is a bit long in the tooth but it’s still running after seven and a half years, and I don’t think this is the right time to be buying a new iMac with rumours of a new model flying around. Besides, I still use software (Dreamweaver and Audacity to name but two) which won’t run under Catalina.

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I am running Audacity 2.3.2 fine with Catalina (10.15.3).


I’m surprised you didn’t just get a 1TB Samsung external SSD and use that as the boot drive. Not really expensive and these drives are fast. I had a base model 21.5 iMac with the world’s slowest HD that my wife used. Doing updates and maintenance on the system was so horribly slow that I finally just got the Samsung SSD and booted off that drive - it made the system much more responsive.


A post was merged into an existing topic: Your Mac Can No Longer Listen for Aliens, but It Could Help Cure COVID-19

That’s exactly what I did, and apart from slow boot and shutdown times, it seems to be working perfectly.

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I wonder if you could just delete all of its partitions, so there’s nothing to mount.

But I suspect that would end up causing the Finder and/or Disk Utility to present its “would you like to format a new drive” dialog every time you log in.

I wonder if there may be some other option to make the system ignore the drive.

A post was split to a new topic: Thoughts about buying a new iMac now?

The “Damaged Installer” results from an expired certificate. It may not always be an option to download a new installer. One solution is to change the date on your Mac to the date that’s on the installer. Get Info on the version of Install macOS xxx and look at the Modified Date. Set the System Date to that date. In Tools select Terminal and in Terminal firstly enter date and you will get the current time and date looking like this: Sat 2 Nov 2019 12:48:47 AEDT. To change it to 14 June 2019 at 12:24, the date I downloaded my last version of Mojave, you would enter: date 061212232019, then return to the Installer and it will work. I have used this trick to install old systems like El Capitan on old hardware and it is reliable.

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This isn’t all of the problem.

As @adam pointed out above, I downloaded a fresh Mojave installer from Apple just the other day and while it ran from my internal SSD boot volume, it refused to launch from an external HDD and instead gave me the usual damaged installer error. This is not just an expired certificate / date issue. There’s obviously more to it.

I’ve been pondering this too, but as far as I can imagine, the only way is a physical disconnection. And if you’re going in, you may as well replace the bad drive.

Just a few weeks after I bought my beloved 9600 Mac it was announced that the much anticipated, soon to be released OS X would only run on Intel Macs. Because it ran on RISC chips, for years I was shut out of upgrades and new applications. This became an even bigger bummer when soon after prices on all RISC Macs began to drop dramatically. As good a machine as it was, and it still has a place of honor near my desk, it became almost obsolete shortly after its birth. Although my very ancient MacBook Pro has been slowly but steadily manifesting signs of imminent death and its OS hasn’t been upgradable for years, I’ve been holding out for an A series replacement. My husband is hanging on with his MacBook Pro for the same reasons.

My advice is to stick it out unless you cannot avoid waiting. If you don’t like the A series Macs when they are released, it’s likely you’ll be able to get a better price on a current model.

Samsung literature for the T5 says, “Even when using USB 3.0 connections, T5 may not perform well if your system does not support UASP (USB Attached SCSI Protocol). Please make sure that your system supports UASP.”

I’m reasonably confident that my 2015 MacBook does not support UASP (since I can find no mention of UASP or SCSI in the USB portion of the System Report). How much “not perform well” am I likely to see? (Note that I would be buying a T5 disk for a Macintosh to be named at a later date, but using it with the MacBook until that later date.) Thanks.

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Yes, deleting the whole drive might work, and I’ve found a couple of web pages which give instructions on that. The fstab method unmounts the drive at some stage in the boot process but earlier in the process, the drive mounts. I think that’s where the problem occurs when updating the operating system (and sometimes when doing a security update). I think that the request to format the drive would probably come later in the boot process but I can’t be sure of that. I’ll need to think it through - it might be safer to open up the iMac and take out the HDD.

There’s never a right time to buy a new computer, other than when you need one. The fault with mine is not down to Apple (other than a poor choice of supplier) - it’s the Seagate 3.0GB drive which is known to be prone to failure. If it’s any help, I will definitely buy another iMac after this one (it replaced the previous generation of iMac 24 inch) but the design (at least on the exterior) hasn’t changed in over ten years and it must be nearly time for a redesign.