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Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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Using a 128 BLADE with a 2TB SSD

I was just wondering if anyone had feedback on fusing a 128 BLADE with a 2TB SSD.

I actually have a 2017 iMac, into which I just put a 2TB 950 EVO, replacing the 2TB HD that was previously there. Right now I have the 2TB SSD fused with the 128GB NVME blade, but the read/write speeds are hovering around 500… which is not quite what I was hoping for

NOTE: I actually think the regular HDD 2TB fusion drive crushes this, in benchmark tests I’ve seen on YouTube… at least early in the tests, tho obviously does decelerate to normal HDD speeds over time… but on the BLADE+SSD fusion set up, the max and consistent speed seems to be the SSD speed.

I’m curious why an NVME+SSD fusion drive would be SLOWER than the HDD fusion setup. Any thoughts?

Reading your exchange above, I’m thinking perhaps better now to use the 128GB for booting, and the SSD for the home directory. But I remain curious as to why the NVME isn’t kicking in at least a bit, in my benchmark tests.

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It makes no sense to create a Fusion Drive set with two SSD’s. The concept of a Fusion drive was to use a smaller SSD with a slower HDD to get a cheaper storage solution than getting a larger more expensive SSD. At the time it made sense as larger SSD where still very expensive.

The problem here is you would be wasting the blade SSD’s benefit as the I/O difference between the SSD’s is so little.

Configuring the drives as discrete drive makes more sense! then you can use the Blade SSD as your boot drive & OS, leave your Apps on the SATA SSD with your data.

If you really want speed! The better solution would be to create a external RAID drive set using SSD’s. That way you are able to use more of the I/O channel in this case Thunderbolt 3.

Here’s the skinny on the I/O connections:

  • SATA III - 6.0 Gb/s
  • Blade PCIe x4 slot - 7.5 Gb/s (8 GT/s)
  • Thunderbolt 3 - 40 Gb/s

These are what the channel can offer the device it’s not what the device connected can in fact do! As you’ve discovered the difference between the SATA & PCIe SSD is not that much! Thats because the SSD’s are not as fast as the channel connection they are using.

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Thank you for this explanation. So, I have broken the fuse between the drives, and made the 128GB NVMe the boot drive, with the SSD as the location for the home folder. In this configuration, the OS and the apps (so far) are taking up 48GB, leaving me 78GB. This is fine for now, but I think it will run out of space here, quickly.

Interesting to note the difference in the speeds, on a 5GB transfer:

* The ‘blade’ is 520-750+ write, and 2495 read

* The SSD is 500 up and down

Am I misunderstanding your data on the I/O connections? If the SATA III is supposed to get 6.0 Gb/s, and blade is only 1.5 faster, then how come my ‘read’ speed on the blade is almost 5 x faster than the SSD? (apologies if this is an extremely ignorant question!!).

One other question:

Seen a number of discussions of people upgrading NVMe drives. Mine is 128. Ideally want more like 500, or even 1TB. I know it is not recommended but, if I could get a professional to do it, what model of NVMe drive would I need?

Thank you!


You are correct the difference here between the SATA & PCIe connections is only 1.5 Gb/s. But thats the theoretical limit, not the true limit of the devices connected! Thats were the protocols used have a big bearing. SATA is quite heavy whereas NVMe is very light. Don't forget the SATA based drives by their architecture can't really go beyond 560MB/s (4.48 Gb/s) Read & 550MB/s (4.4 Gb/s) Write as they have a limit of transactions that can be done at one time. The size of the SSD will also effect things the smaller SSD's are slower and the larger SSD's are faster.

Think of it like a highway the speed of the car does not need to be the as fast as the highway can support. This is the part many people fail to realize. So if the road has a speed limit of 80 MPH I can still drive my car at 50 MPH on it. And maybe that the limitation of my car so it can't go to the max the road can support.

Now lets look at that same highway if I have 4 lanes and I have four cars running in tandem I can move more people within the same window of time. So a PCIe SSD which has 4 lanes will move almost twice as much as a 2 lane PCIe SSD. We can push this even more so using a external RAID box which supports PCIe SSD's. So if I have 4 SSD blades each has 4 lanes I could theoretically push 16 lanes of data at once! Thats why the external RAID box is beneficial!


Thank you. That's actually a really clear explanation. I didn't understand the "lane" concept, prior to now.

Back to the question of upgrading the NVMe, tho. While a RAID might be an option, if we can assume for now that I would just be upgrading the internal PCIe, what spec/model would work inside a 2017 27" iMac?


Yes, I always recommend people forgo the SATA drive and make the leap to the PCIe drive when they buy a new system and need performance.

Upgrading afterwards can be a bit tricky! It's a lot of work as you need to take the logic board out to get to the drives location (Apple's poor design!) The other rub is the cost! These drives are just hard to find and are costly! Which is why I aim people to the still better direction of the external RAID as you'll end up being in a better position moving forward.

Here's what you'll need for the blade SSD

- Custom Samsung SSPOLARIS 1 TB SSD

- Custom Samsung SSPOLARIS 2 TB SSD

Or... OWC - Express 4M2 TB3 RAID box and Samsung 860 EVO M.2 SSD's you'll need at least two. Which will in fact be cheaper!


This is really, really helpful. You have no idea how hard this information is to find, online. So, I will definitely consider the RAID approach. Not sure yet what I will do. But what I am thinking about right now is getting a 500GB PCIe drive, and using it as my main drive, including the Home folder. This will keep it as the main functioning drive for my audio and video processing work. Then I can relocate my iTunes, Photos and other more storage intensive stuff, to the 2TB SSD.

Much to think about. Thanks.


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