Chosen Solution
Hi, I want to upgrade a 27” 5k 2019 iMac that has a fusion drive in it. With the Big Sur update, it became horribly slow. The fusion drive was probably a poor choice from the beginning. It’s my mom’s mac and she was scared she wouldn’t have enough storage with a 250GB SSD, even though I explained to her that internal SSD + external thunderbolt drives were the best choice. So I guess I have two options: A/ Removing both the fusion drive SSD and the drive and putting a Sata 2.5” SSD in place of the original HDD as the main internal drive. I think 2019 iMacs have 2,5 format HDDs, so I suppose putting a 2,5 SSD wouldn’t require any adapter. It’s the choice I like the least as NVMe M2 SSD has dropped in price and are faster than SATA SSDs. B/ Removing both the fusion drive SSD and replacing it with an NVMe M2 SSD (and also removing temporarily or permanently the HDD as it is linked in a fusion drive setup, and needs at least to be “unlinked”. I think I might just dump it all together for convenience.” I like this option better, but I have several questions: 1/ Regarding data migration, I read here that since the system partition is APFS, it’s not possible anymore to just clone the whole partition with Carbon Copy Clone to the new NVMe M2 SDD plugged in externally in some kind of enclosure. This puzzles me because CCC states that it can work with APFS and I know for a fact that until Mojave at least, it did a good job cloning not only the data but a recovery partition as well. I’m quite reluctant to use the data migration tool provided by Apple, which relies on Time machine if I’m not mistaken because I had issues with it in the past… @danj, you seem to know a lot about this, can you please confirm it to be that using CCC for this isn’t possible anymore, given that the version of Mac OS used here is Big Sur? 2/ Regarding the hardware, I saw videos of guys doing basically this, but it seems that an adapter is needed. Which ones are known to be working for this upgrade? 3/ Also, regarding the M.2 SSD that I would use for this, I was thinking about a Western Digital SN770 NVMe because I read on a Hackintosh forum that these were always compatible with recent Macs, as WD is now the main company that Apple relies for its production concerning SSDs. Is there maybe a more natural choice for this upgrade? Thank you in advance for your help :)
I use Apples TimeMachine and Migration Assistant. Apple has not released the deeper details on how to properly ‘Clone’ APFS. What you are doing with CCC is the older block style of clone copying Which is a bit of a crapshoot! They assume all of the blocks are clean and none are an located spare block from the reserve. Then to add to it if you enabled encryption all bets are off! I haven’t used any cloning software on startup drives for years as I want to do the job as quickly and as efficiently as possible as time is money and I don’t want to deal with the mess afterwards. But just like playing Russian roulette are you willing to play? FYI - A Fusion Drive is physically two drives the blade SSD (Caching) and the SATA HDD drive (Data). Now the next point I don’t recommend using M.2 SSD’s in iMacs as they are fussy! Given how deep you need to go in, it’s best to stick with either a real Apple or OWC SSD drive they work and are reliable and yes a bit more cost. Frankly, I don’t think your Mom is pushing the system that hard, a SATA SSD will more than likely meet her needs. So get a SATA to USB or Thunderbolt adapter/drive case to hold the new drive and just run Migration Assistant to migrate everything over to the new drive, check it by booting up under it and then pull both drives and install the new drive - Done!
@rafaeru - have you run the onboard diagnostics to see if an error message popped? I would do that first before assuming you have a drive issue given this added details. Restart the system and press the ‘’’D’’’ key to enter. Let us know what you discover.
