Modernizing the Fusion Drive: PCIe SSD with fast (~3GB/s) & slow (~1GB/s) flash memory

[Hexley]

Fusion Drive is Apple's implementation of a hybrid drive. Apple's implementation combines a HDD (~200MB/s) with a SSD (~3,000MB/s) and presents it as a single Core Storage managed logical volume with the space of both drives combined.

What if the "all SSD" Fusion Drive be PCIe-only SSD but with fast (~3GB/s) & slow (~1GB/s) flash memory.

macOS automatically manages the contents of the logical drive so the most frequently accessed files are stored on the faster flash memory, while infrequently used items move to or stay on the slower flash memory.

Not ideal if you're doing 4K video editing and other high throughput applications but good enough for everyone else who are looking for a lower $/GB ratio and do not mind slower throughput for files they use infrequently.

I broached the topic of a PCIe+SATA SSD Fusion Drive but it adds parts and complexities that would raise cost. So why not keep to PCIe-only but with 128-256GB faster flash memory & 1-8TB slower flash memory.

Other than the iMac this could be applied to the Macbook Air & Mac mini

This year PCIe 4.0 SSDs are coming out with up to ~7GB/s throughput. Exciting times...

 

[Juicy Box]

I am assuming you are talking about just on new Macs, as people have been doing PCIe SSD and SATA SSD Fusion Drives for a while.

I have also thought about Apple replacing the SSD+HDD Fusion Drive for an all SSD Fusion Drive, and have mentioned it on threads.

It just makes sense, as SATA SSDs prices continue to drop, but NVMe SSDs seem to still be pretty expensive.

I guess the price difference between SATA and NVMe isn't as drastic as HDD and SATA back in 2012 with the launch of the Fusion Drive, but I still think it would be worth considering.

Maybe Apple could finally drop the HDD.

Apple could call it the Fusion Dirve 2, Fusion Drive Pro, Fusion Drive Max, Super Fusion Drive, or the Super Max Fusion Drive Pro.

Apple's implementation combines a HDD (~200MB/s)

If that...
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What if the "all SSD" Fusion Drive be PCIe-only SSD

Missed this part.
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I personally couldn't picture Apple doing an all PCIe solution, just because the price difference between the faster and slower PCIe would probably not be as dramatic as SSD and HDD prices were back in 2012.

Also the real world benefits would mostly go unnoticed by most users, especially when you compare it to the 2012 Fusion Drive.

But, I guess it could happen.

 

[kohlson]

For me, evaluating the cost/benefit doesn't show that much of an advantage. And I am speaking from what I can do (parts off the shelf), not what Apple can do (engineering and new product development) <-- because they can do whatever they want.

There are variations on comparing products (cell technology, for example) but a good 1TB SATA SSD is US$150-ish. And a NVMe SSD of the same capacity is about 20% more. Yes, the NVMe is almost 6x faster link speed, but will that matter in day-to-day work flows.

The idea for the original Fusion is still compelling. Most of your data is static. Don't put all of it on high price/performance media - just the part you often use. That same $150-ish buys, at retail, between 4 and 8 TB of spinning storage.

 

[hwojtek]

MacOS automatically manages the contents of the logical drive so the most frequently accessed files are stored on the faster flash memory, while infrequently used items move to or stay on the slower flash memory.

Not exactly "automatically".
Apples Fusion Drive makes use of the "medium type" as seen in System Report, to determine which drive is faster.
In case of two drives reporting "solid state", it may be up to the BSD name (/dev/disk[number]) where the lower number will be considered "faster", but apparently MacOS doesn't do anything in this case. While creating a Fusion Drive off two SSD drives, however, user may point the OS to the faster disk. This commands will create an APFS Fusion Drive from two SSDs, one faster and one slower:

diskutil list

(make note of the BSD names of the two disks, they will most probably be disk0 and disk1, compare their parameters to make sure which is which. We call the faster one "main", the slower "secondary")

diskutil cs create Fusion disk0 disk1

(this creates the main Fusion Drive - logically merges the two)

diskutil apfs createContainer -main disk0s2 -secondary disk1s2

(this creates an APFS container on the merged structure, pointing the OS which disk is the faster SSD).

Now just create a volume as usual in Disk Utility and you are good to go.