External SSD for macOS (iMac 2019 27")

The EtreCheck report shows that that 27" 2019 iMac has a 1 TB Fusion Drive.

Since this is a 27" iMac, the hard drive should have a full-size 3.5" desktop mechanism, and reasonable speed – for a hard drive. But Apple really skimped on the amount of SSD space in 1 TB Fusion Drives that year. The 1 TB Fusion Drives only included 32 GB of SSD space (instead of the 128 GB in the original 1 TB Fusion Drives).

The EtreCheck report shows that that 27" 2019 iMac has 64 GB of RAM. If the Mac saves snapshots of RAM when you put it to sleep, and restores them when you wake it (as one Mac news article suggested), that means there isn't enough SSD space on that Fusion Drive to hold a snapshot of RAM. At least half of any snapshot would be written to, or read from, the hard disk – thus making Sleep and Wake take longer.

That Mac needs an external startup SSD. Even a USB 3 / SATA one would likely beat that Fusion Drive, but you can get USB-C (USB 3.1 Gen 2) / NVMe SSDs for not much more than USB 3 / SATA ones, and they seem like they'd be a good compromise between cost and speed. In addition, they probably wouldn't face thermall/cooling issues that are quite as extreme as those of Thunderbolt 3 SSDs.

ps. If you really want TB3 speed, take a look at the 1.0TB OWC Envoy Pro FX. It contains an OWC Aura NVMe SSE but it's also $280.

What apps are you using that demand 40GBps drive speeds?

IMHO a good external USB 3.2 Gen2 USB-C enclosure with a good SATA SSD inside would be completely satisfactory for running a 2019 iMac. I have a 2019 27" 3.6GHz i9 iMac with an OWC Mercury Elite Pro Dual with 3-Port Hub containing Samsung 870EVO SSDs and its performance is fine.

A 2019 27" iMac has the following ports:

• 2 USB-C ports compatible withThunderbolt 3 (up to 40Gb/s) & USB 3.1 Gen 2 (up to 10Gb/s)
• 4 USB-A ports compatible with USB 3.0 (up to 5GB/s)

The Kingston & Corsair M.2 SSDs would both be overkill.

But if you are wedded to using an M.2, look at the OWC Express 1M2 Enclosure. You can get just the enclosure or equipped with a 1.0TB OWC Aura Ultra IV PCIe 4.0 NVMe M.2 2280 or larger SSD.

Please post the full Etrecheck report according to these directions:

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and use the Additional Text button to paste the report in your reply.

Then we can examine the report and see if we can determine the cause of the problem is any 3rd party software.

Yeffersson wrote:

Why it would be overkill with Thunderbolt 3, which supports up to 40gbps? Especially when the Kingston XS2000 is limited to only 20 gbps?

Don’t get me wrong - I’m not arguing. I just genuinely don’t understand.

The Kingston XS2000 is USB 3.2 Gen 2x2, not Thunderbolt. Its potential 20Gbps performance would be capped at 10Gbps by your iMac's USB 3.1 Gen 2 10Gbps port.

Regarding the Corsair MP600, you could put it in a Thunderbolt 3 enclosure if you can find one that is reliable and meets your heat dissipation requirements. But the only one I found that I thought met your requirements is the OWC Express 1M2, and it's not Thunderbolt ... it's USB 4, which is also capped at 10Gbps by your iMac's USB 3.1 Gen 2 10Gbps port.

BDAqua wrote:

We're not seeing them...

It's there in the other thread that the OP linked.

But for some reason the posts in that thread are not showing up in proper date order. Look for his short post dated "July 28, 2024 12:59 pm in response to HWTech." All it has is the Etrecheck report. Sometimes it shows up on page 1 of the thread, other times on page 2. Just not in the proper place either way.

👍 

We're not seeing them...

He posted the reports to another topic: here

It's convoluted. Try here: Problems with installing macOS Sonoma 14.… - Apple Community

The Corsair MP600 Elite 2TB has a 4-lane PCIe Generation 4 interface. It has sequential read speeds of 7000 MB per second and writes of up to 6500 MB per second. (Both obviously best-case.)

https://www.corsair.com/us/en/p/data-storage/cssd-f2000gbmp600enh/mp600-elite-2tb-pcie-gen4-x4-nvme-1-4-m-2-ssd-cssd-f2000gbmp600enh#tab-techspecs

A Thunderbolt 3/4 or USB4 40 Gbps port has a raw data rate of 5000 MB per second before overhead. (There will be overhead.). So an external enclosure is likely to bottleneck the SSD a bit. You would get the fastest speed out of it if you had an internal M.2 PCIe slot that supported PCIe v4, into which to install it.

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The Kingston XS2000 has a USB 3.2 Gen 2x2 interface, and requires USB 3.2 Gen 2x2 to reach maximum speed. Macs don't support USB 3.2 Gen 2x2, so the connection will fall back to USB 3.1 Gen 2 speed ("up to 10 Gbps", a.k.a. "up to 1250 MB per second").

https://shop.kingston.com/products/xs2000-external-ssd?variant=40686324875456