Chosen Solution
Brief: Fusion Drive is marked FAILING, per S.M.A.R.T. . I tried replacing internal HHD with SSD - but, wouldn’t power on. (This caused a cascade of issues - detailed below.) Returned HHD, now currently working - but, I need a permanent solution! Detail: This is a very long story, so I’ve tried to truncate it with bullet points… Everything has been working perfectly for 3+ years, other than slow restarts, slow Time Machine, slow cloning, etc.Went to install a new OS. Failed, due to “S.M.A.R.T. status of “FAILING” Fusion Drive.Confirmed “FAILING Fusion Drive” via Disk Utility.FYI - Disk Utility only shows “Fusion Drive” - no SSD / HHD (see picture). Is this normal?
Cloned 3TB Fusion Drive with Super Duper to external Crucial 2TB SSD.Disassembled iMac per iFixit instruction & YouTube videos. Replaced internal HHD with SSD with OWC kit. Reassembled.iMac wouldn’t start up! (Skipping hours of troubleshooting here - SMC, PRAM, reseated Ram, multiple power cords, multiple outlets, etc.).Reset iMac to the original configuration. iMac wouldn’t start up. (Skipping hours of troubleshooting here…)Took iMac to Simply Mac (local Apple Preferred shop). iMac start right up (WTH?!). Ran diagnostics. No issues. Passed S.M.A.R.T. Restarted several times.FYI - For 2 days, I ran a secondary iMac from the cloned SSD, via an external enclosure. This is how I know that the new cloned SSD was not the issue.Took iMac home, swapped internal HHD with SSD/OWC kit. iMac doesn’t start up. (%$#@). Reset with the original config. iMac doesn’t start up (no response). (Skipping hour of troubleshooting here.)Reconfig back to new SSD/OWC kit. Took iMac back to Simply Mac. iMac starts up (!) - BUT, shows no OS (black screen with circle / slash / “no” icon. Ran diagnostics in Recovery Mode. This time, only the internal SSD blade shows up. However, everything else checked out (hardware, ram, etc.)Took iMac home, configured to original setup. iMac works as normal again. (Thank God! Using it for 2 days now…) Updates: DriveX has confirmed that the internal SSD, not the HHD is what is failing.
(not sure what this means. It’s from the Failing SSD.) Current Setup: 2017 27” iMac with Fusion Drive 128 MB SSB Blade (Failing)3TB HHD (cloned to replacement 2TB SSD)64 GB Ram External Drives 4TB HHD RAID (Working Files, Stored Media)6TB HHD (4TB Raid Backup / 2TB System Backup — clones)4TB Time Machine (will replace soon)External Desk Fan - took keep externals cool Additional 2TB SSD - purchased to replace 3TB HHD Fusion Drive * Additional Notes: I use my machine for Graphic & Web Design. So, significant use of Adobe Photoshop, Illustrator, InDesign - but not much audio or video. However, I do stream movies, youtube, etc. a LOT. Conclusion: Simply Mac called Apple and they gave the same theory we came up with: Internal SSD blade is what is failing, not the HHD. This is what is causing the SMART FAILING. This is also what is causing the intermittent no-startup. Apple suggested I split the Fusion Drive to solve the problem. But, I don’t know what new issues this will cause, as well as I’m concerned with all of the current issues I’ve had (not starting up). Questions: How can replace the Fusion Drive with the new Crucial 2T SSD, with the least amount of drama?!Do I need to split the Fusion Drive, and if so, what issues will that cause/fix?Do I need to physically remove the internal SSD blade, so that it won’t cause an issue? Or, can I bypass it somehow?Can I / Should I replace the internal SSD blade? (It’s not too expensive, but it’s a major teardown - which may cause additional issues.)What is the actual procedure I need to take? (Link?) My biggest fear is that I will get stuck in the same no-startup scenario again. I HAVE to have my iMac for work. But, with the SMART failure, I’m concerned with even needing to reboot! Additionally, I need to make an OS update, as being on 10.15 is keeping me from updating other items, which I need. @danj — this is extremely helpful! Thank you. In response to your 12/14/21 Update (I’m not sure where to post this): I’m a bit intimidated about replacing the SSD Blade. (I guess I should be!) But, I’m confident I can do it. I’ve worked on the internals of several macs, as well as iPhones, etc. Additionally, I wasn’t impressed with our local Mac shop option - I had much more experience than them. :/ I think I’m going to go with this SSD Blade (due to price and size): https://www.amazon.com/Fledging-Included… I can follow the iFixIt procedures on physically replacing the drive. (Thanks for sending!) My main concern is this: I had originally cloned the Fusion Drive to an SSD, and then physically replaced the HDD portion of the Fusion Drive — which caused all of the issues above (no startup). Now I realize that it’s the Blade that was failing, not the HHD — So now I need to replace the Blade (as we discussed). I’m just not sure about the software procedure and the HHD replacement. A. Can I simply clone the “Fusion Drive” and then replace both the internal SSD Blade AND the HHD (with 2TB SSD)? And, if so, when I restart, will it look the same (just faster)? B. Or, do I have to replace the SSD Blade, but leave the slower HHD? C. Most Importantly, do I need to do anything else, such as “slip the fusion drive” beforehand? Anything else? Thank you so much for your time and patience! Update (12/27/2021) I was able to fix my iMac with the help of @danj ! In a nutshell: Made clone backup of complete Fusion Drive to a 2TB SSD with swappable USB 3 external enclosure.Replaced SSD Blade with a new OWC 1.0TB Aura Pro X2 SSD.Replaced internal HHD with 2TB SSD, using the OWC HHD to SSD Kit.Started up from new internal 2TB SSD.Initialized and installed the newest macOS on the internal 1TB SSD Blade.Used Mac’s Migration Assistant to move over the bare minimum user files, preferences, etc. (No apps, no photos, no music or movies, etc.)Restarted with new 1TB SSD Blade. Hand-installed Apps. (See why below)I will make another backup/clone of the 1TB SSD Blade/main system for safekeeping, and then…Wipe internal 2TB SSD and use it as my working volume. (I’ll store photos, music, archived client files, etc. on a 4 TB Raid external enclosure.)I’ll also make a fresh Time Machine copy of the main system since my current copy hasn’t been reliable. Thankfully, Hard Drives are cheap! Why not use a Clone, Time Machine, or a complete Migration Assistant for Main Drive? I’ve been migrating profiles and apps since Mac OS 9! I wanted (mostly) a clean slate with this setup. I had one app that was dated 2005! Results: The 27” 2017 iMac is now running 5X faster!No issues with startup, caused by failing Fusion Drive (SSD Blade)! Items used: OWC 1.0TB Aura Pro X2 SSDhttps://www.amazon.com/gp/product/B07QDP…(Note: the first one they sent me was USED! I had them resend a new blade.) OWC SSD Upgrade Bundle for 2012-2019 27" iMacs, 120GB 6G SSD…https://www.amazon.com/gp/product/B076KX…(OWC’s SSD prices are ridiculous, so I got the smaller SSD with this kit and am using it on an older 21” iMac) Western Digital 2TB WD Blue 3D NAND Internal PC SSDhttps://www.amazon.com/gp/product/B073SB… Sabrent USB 3.0 to SATA External Hard Drive Lay-Flat Docking Station for 2.5 or 3.5in HDD, SSD https://www.amazon.com/gp/product/B00LS5...(I have two of these things and they work great!)
First the Fusion Drive is really two distinct drives so when you state the Fusion Drive has a S.M.A.R.T. error of the drive failing that doesn’t tell us which physical drive is failing: the primary (HDD) or the cache (SSD). Most of the time it’s the HDD that fails due to its mechanical nature. The only time I see the Cache SSD fail is when someone is doing quite a lot of data churn like music or video production, Fusion Drives are not well suited for that. There are some tools which can read directly from the physical drives the S.M.A.R.T. data so you can ID which is in trouble. I use this app to check things DriveDx take a snapshot of the drives data and post it here for us to see Adding images to an existing question Reference: List of S.M.A.R.T. Errors for HDD and SSD While this may sound extreme often times I can get a little more life out of the SSD by reformatting it so the blocks that have failed are quarantined by the SSD’s controller and over provisioning can be used to back fill the space. What is your workflow? As that can help in aiming you to the best setup for your needs. Update (12/14/2021) @endura - Well you are running your system hard! At this point your data (HDD) is OK, so at this point its just a matter of replacing the NVMe/PCIe drive. Review this guide iMac 27" 2017 Blade SSD Replacement so you know what you’re getting into, I’m guessing this maybe a bit much for you to fix. So lets review what Apple will do they will just replace the cache SSD with the exact same unit and rebuild your Fusion Drive which is not a good solution for you. They won’t put anything else in. If you go to an independent Mac shop they can put in a different drive! Which would be the better direction for you. I would go with the minimum of 480 GB OWC Aura Pro X2 SSD or if you can swing it I would go with the 1 TB OWC Aura Pro X2 SSD Here we are going to setup a dual drive config the NVMe/PCIe drive will become your boot drive hosting your OS and your Apps. We want to leave 1/3 of the drive as free space so your OS and apps have room to work. If you get the larger drive you’ll use some of the space for your active Adobe Photoshop, Illustrator, InDesign, Web Apps projects. Your HDD will host your finished work and media files.
