Late 2015 iMac SSD Upgrade Advice (Internal or External?)

[rickpoet]

Hello, I know this issue has been covered in a lot of different ways in other posts...I've read through a lot of them but haven't found anything definitive for what I'm looking for...so sorry if I missed it.

I have a Late 2015 iMac 27" (i7, 17,1) with a 2TB Fusion Drive. I'd like to update from the internal hard drive to a 4TB SSD. From what I'm gathering my options are:

1) Use an upgrade kit and do the more complex disassembly to replace the stick SSD drive with the size I want. (with an adapter.)

2) Use an upgrade kit and do the less complex disassembly to replace the SATA spinning hard drive with the SSD (with 2.5" to 3.5" adapter.)

3) Use an external drive of some kind with the existing Thunderbolt 2 port.

I'm leaning towards 3 because of the ease but I don't want it to be super slow. If I did #3, here are my questions:

1) What's the best way to do this (which products and adapters) to get the best speed out of the Thunderbolt product.
2) I've seen references to people not being able to use a drive like this in the TB2 port as a boot drive. Am I going to run into this issue?
3) Can I disable the original internal SATA spinning dive if I make the external TB2 drive the boot drive so it doesn't spin up, cause fans to go etc. (or if I just don't use it will that even be an issue?)
4) Will any variation of an external Thunderbolt SSD indeed be faster than replacing the internal SATA drive with an SSD.

Thank you so much in advance for your recommendations!

 

[roadkill401]

I have a late 2014 iMac 2K. It has a smaller 512gb SSD drive internal, but I have a OWC Thunderbolt2 mini bay attached that houses several 2.5" SSD drives that I boot from all the time.

Is it slower than the internal SSD? YES, but the internal one is blazingly fast. But it is far faster than my Mac Mino that has a Fusion drive inside it. There is no issue with booting off a TB2 connected drive. I have done it off a regular Lacie hard drive and off the Thunderbay drive. Right now I have a version of 10.13 installed on of the other thunderbay drives that I use for music production. I also have my bootcamp Windows10 installed onto it's own SSD drive also inside the Thunderbay.

 

[rickpoet]

Thanks for the reply. Slower than the internal SSD attached to the PCI port on the back of the main board I get, but would an external Thunderbolt 2 SSD connected drive be slower than the internal SATA which (in my system) is the original spinning platter drive part of the fusion drive?

 

[smirk]

Thunderbolt 2 is 20 Gbps.

SATA 3 is 6 Gbps.

The bottleneck here will be your SSD drive.

 

[rbart]

I have upgraded mine with a SATA internal SSD.
It's not difficult and it's fast.
Except in benchmarks, you won't notice the speed difference with an NVME SSD.
It's very hard/expensive to find TB2 enclosures to have faster speed then internal SATA.

 

[rickpoet]

Thanks. I'm probably going to go with the internal SATA option. I haven't had much luck, as you can guess, finding a good TBT external option and then there seem to be issues with allowing TB2 to work as a boot drive.

 

[UrsoSeattle]

I just put a 2.5 Samsung SATA SSD in a late 2015 21.5 iMac. Night and day, it's a totally usable machine... now...

Seal cutting wheel, replacement adhesive, suction cups and drive all obtained from a giant online retailer.
A fussy smallish TORX screwdriver is needed but was in a tekton kit I had. I think it was a t8.

Lots of videos on the web.

What most videos do not show is putting the new adhesive on the newly cleaned surfaces. There are little guide holes in the frame of the mac that lined up with holes in the new tape. I used an awl to guide the new tape to correct registration hole and it was fairly easy to to a clean job.

With the stock SATA drive, the machine was punitive to use. Performance now is plenty for my purposes for this machine.

~S

 

[DadofEandZ]

I just put a 2.5 Samsung SATA SSD in a late 2015 21.5 iMac. Night and day, it's a totally usable machine... now...

Seal cutting wheel, replacement adhesive, suction cups and drive all obtained from a giant online retailer.
A fussy smallish TORX screwdriver is needed but was in a tekton kit I had. I think it was a t8.

Lots of videos on the web.

What most videos do not show is putting the new adhesive on the newly cleaned surfaces. There are little guide holes in the frame of the mac that lined up with holes in the new tape. I used an awl to guide the new tape to correct registration hole and it was fairly easy to to a clean job.

With the stock SATA drive, the machine was punitive to use. Performance now is plenty for my purposes for this machine.

~S

Hi UrsoSeattle, I am thinking of doing exactly the same on my late 2015 27inch Imac to replace the fusion drive (partly because after 5 years its slow and inexplicably annoying as a machine and its a reinstall anyway). I'd read that you need to deal with the fan speed sensor as well - how did you do that? Is it SATA or SATA 2 or 3 - I am not sure of the difference?
thanks

 

[Khaleal]

1. The internal SSD is your best option performance wise, but it involves almost completely disassembling the iMac. Also, I don’t recommend a 3rd party nvme ssd for any iMac older than mid 2017 as they tend to have sleep/hibernation issues in this configuration. So if you’re thinking of installing an internal blade ssd, consider buying a second hand original apple ssd off ebay (but i doubt you’d find anything bigger than 1tb).
2. The 2.5 ssd is easier but you’ll be still limited to sata3 speeds (around 500mb/s), also it’s not much easier than the blade install, as you’ll need to remove the display either way (which is the hardest part the most time consuming). This option would give you the ability to install 4tb ssds, without compitablity issues (like sleep etc). Note that you don’t need a thermal sensor adapter for your model.
3. It’s much slower than internal blade ssd, but it’s much better than the spinning hard drive, and very simple to install.