Recommend 2TB SSD for 2017 Retina iMac OS boot drive

an internal SATA SSD replacement (upgrade the failed HDD) is a minor shop upgrade

and you get the dust blown out of the machine

i recommend a quality part like the Samsung 870 EVO or 860 Pro SATA SSD

for comparison:

an internal SATA SSD will provide sustained 500 MBs write/read speed

the original fusion HDD provided 80 MBs write/read speed

the ACASIS TB3 will provide the fastest read/write speeds your machine can deliver (2400 write, 2600 read) see the screenshot -- that's a bit faster than Apple's original internal Flash SSD

UNFORTUNATELY this is not a good time to be buying SSD (or RAM) for the crazy 2026 price spike...

why mess around with SLOW usb external on a 2017 that supports Thunderbolt 3 SPEED

ACASIS 40Gbps M.2 NVMe SSD Enclosure, with Cooling Fan, M.2 Enclosure TBU405 Pro

Samsung 990 Pro SSD (for external boot system in enclosure) i don't cheap out on boot SSDs

WD_BLACK SN850X or WD_BLUE SN5000 (for backup, TimeMachine, clones, data storage)

EASILY swap NVMe SSD in this enclosure

this enclosure also works on USBc, USB3, USB2 (but at those speeds)

Check with OWC (MacSale.com) for which of their many external SSDs would best fit your workflow and budget. OWC is considered to be the premier online Mac hardware supplier by most of the experienced users here.

An example is 2.0TB OWC Envoy USB 3.2 (10Gb/s) Bus-Powered Portable NVMe SSD.

old toad

>>An example is 2.0TB OWC Envoy USB 3.2 (10Gb/s) Bus-Powered Portable NVMe SSD.

That’s current $499 USD?

what read/write speed do you get out of that external USB ssd on Mac TB3 — I know the theoretical published, but I guess it’s considerable less than half 2400MBs tb3 Mac hardware?

the Acasis tb4 enclosure is $100 current, including tb4 cable

the Samsung 990 Pro 2Tb m.2 ssds I bought in Nov-dec were $159ea - current $299 ea

thats $399 ($100 less than the usb Owc external ssd) — and the Acasis runs more than twice the speed (if I recall correctly)

im no fan of OWC ssd or the sealed type of enclosures you can’t easily swap ssds

but There are many workflows — you know — I buy what I have confidence in (price is rarely a factor when my paycheck and rep are on the line)…

All you really need is a decent USB-C 3.2 External SSD to keep that iMac going for a few more years.

Then start saving up for a new iMac or Mac mini and display to replace that vintage 2017 iMac.

https://www.tomsguide.com/best-picks/best-external-hard-drives?

https://10best-choices.com/thunderbolt-drive-for-mac?

https://buyersguide.org/Thunderbolt-SSD-drive/t/best?

yes all that, i started out on the OWC single bay Voyager (USB2 i think) -- replaced it with one of the pictured OWC dual bay enclosures (eSATA i recall) -- replaced that one with a newer model OWC dual bay -- both dual-bay units were flaky for me running two mounted drives in one enclosure crashed my machines

i recently junked my second dual bay and replaced it with a current single bay NewerTech Voyager S3 USB3 SATA drive interface -- i mostly use it for running TimeMachine and clones to HDD

VERY USEFUL TOOL TO HAVE AROUND -- i've used them more than a decade and highly recommend the current USB 3.2 model -- in any case -- those dual-bay OWC SATA are USB 3.2 (5Gb/s) max speed -- SLOW AND STEADY WINS THE RACE -- hard to argue otherwise

i was an early adopter of the OWC Mercury and Pro 2.5" SATA SSDs -- super expensive in the day -- went through about six of them over some 7 years -- eventually junked or sold them all off... wasn't for me (OWC tech support were very tedious and inconsistent for me to deal with, including the dual bay enclosure issues)

i recommend what i actually use -- here is a pile of ACASAS TREBLEET X5 Thunderbolt 3-4 SSD

i have a case of bare NVMe PCIe M.2 SSDs i swap in/out of the ASASIS -- the ACASIS case bottom conveniently flips up with a fingernail and removes, the rubber pin pulls out, the SSD pops up and slides out

the ACASIS wins out for the ease of swapping SSDs -- and the built-in fan

I use a wd sn850x nvme in a tb enclosure but like already noted drives are getting expensive.

-g wrote:

or the sealed type of enclosures you can’t easily swap ssds

I am a big fan of OWC but agree with you about easily swapping SSDs. That's why I have this setup:

I haven't gotten into the NVme SSDs yet, still with the SATA SSDsx. The setups as seen are only 500 Mps but that's fast enough for my work. With my 2017 17" iMac with an SSD boot drive I have a couple of older systems on SSDs to boot into. Even though they were 4 times slower the difference in boot time was not that much different. Any the general operation seemed as fast.

I've had excellent success with OWC hardware and their Customer Support. Their warranties are good and they stand behind them, as least the one time I needed it. They replaced a defective SSD (even though I think I did the messing up) without question.

I haven't gotten into the NVMe SSDs yet and don't know if the adaptors for them to use bare have the speeds that they are capable of.

The one that I linked to is expensive and they've gone up somewhat due to recent tariffs. 😔

As -g points our, this is a tough time for buying SSDs. I bought this drive (1TB) last March (2025) for US$100. Today it is $250.

Does the computer start at all? If it starts, you may be able to check if the Fusion is simply "split." Split means the SSD and the mech drives have lost their software link. The computer technically "runs" but very slowly, often worse than Mech-only speeds. If splitting is the issue, that is an free at-home fix. See:

How to fix a split Fusion Drive - Apple Support

If "slow" is the only issue, you mighty get a bit more life out of the 2017 without spending money.

You're welcome.