I have a late 2015 iMac with a 1 Tb Fusion drive and a 24 gig NVMe M.2 drive in it.
I am looking to upgrade the drives. From what I've read the OS is installed on the Fusion drive. What exactly is the 24 gig NVMe M.2 drive used for? Is it possible to install the OS on the NVMe M.2 drive if upgraded to a larger drive. My plan is to put a 500 gig or 1 TB NVMe M.2 drive in for the OS and a 1 TB SSD for a work/user drive.
iMac 27″, macOS 10.15
Ron2112, I think that the system sees the 24Gig M.2 drive and the 1TB platter as one drive. I asked my local Authorized Support provider about this situation when my 2012 iMac had a HD go bad. It wasn't a fusion drive. It is my understanding that I could put both a NVMe drive and a SATA SSD internal to the iMac to replace the failed HD. I would then have 2 internal drives. I decided to just go with the SATA SSD as the 2012 iMac is getting old. I know MVMe drives are faster than SATA drives but in the real world how much difference are you going to see in performance? Where is the bottleneck in performance. I would also see if ifixit has any videos or guides about this replacement.
Paul
It is my understanding that a Fusion drive is the combination of a spinning HD and a small SSD. I think that is what you are seeing in your iMac. You don't need to replace both. You can either put a large 1tb or 2tb NVMe SSD drive or a large HD. You can't replace a fusion drive unless you can get a fusion drive from Apple. I would replace your fusion drive with a SSD.
Paul
It is not clear exactly what you are wanting to do?
OWC has a few upgrade options for your 2015 27" Fusion Drive iMac model.
see > https://eshop.macsales.com/shop/ssd/owc/imac-27-inch/2013-2019
I am planning to remove the Fusion drive from the system permanently. The Fusion drive is suppose to have a 128 gig ssd and a 1 TB platter drive. I am putting a 1 TB SSD SATA in to replace the Fusion. I would like to install the OS on the NVMe M.2 drive if possible. If not, I would install it on the 1 TB SSD SATA drive. My question was what is the current 24 gig NVMe M.2 drive being used for if the OS is on the Fusion drive?
Good catch Alan, no I totally missed that tit-bit.
Sounds like a lot of money to put into a 6 year old iMac.
Think I'd add it all up, then see if it isn't better to sell and put all the money towards a newer or new pure SSD model.
There you go, enjoy.
The 128 gig SSD on the Fusion drive is hidden the drive does "it's own little thing" to put the most used files on the SSD portion.
A SATA drive has read/write speeds of 500 to 600 Mbps. An NVMe M.2 drive is connected to the PCI Express bus of the motherboard which is a faster bus. Some of the top NVMe drives have read/write speed's in the 2000 to 3000 Mbps range. The Samsung 980 Pro NVMe has a blazing 6900 Mbps!
First of all, the 128 gig is a flash SSD that is part of the Fusion drive. My iMac has a 24 gig "blade SSD" NVMe M.2 attached to the PCI Express bus. Your option "3." is what I'm trying to accomplish. Putting the OS on a 500 gig or 1 TB Samsung 980 Pro NVMe M.2 that will replace the current 24 gig NVMe M.2 drive and also putting a 1 TB SATA SDD in place of the Fusion drive. What I want to know is, after replacing the drives, will that Samsung 980 Pro NVMe M.2 drive be available as a destination drive for a fresh install of Catalina or Big Sur? I have no problem with completely disassembling the iMac!
I have found some answers:
https://forums.macrumors.com/threads/a-list-of-successful-imac-27-2012-2019-ssd-upgrades.2162435/
It appears it is possible to upgrade the only issue with my model is the "sleep" problems.
Yes, probably right!
Considering the "sleep" issues, I think I'll abandon the NVMe M.2 upgrade and just put a good SATA SSD in.
A new iMac is not in the budget and this one still has lots of life left in it.
Leroy, did you notice the footnote in that OWC listing?
I just read an article on OWC website concerning Aura Pro X2.
Thanks for the reference.
NVMe M.2 drive install
