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

Discussion in 'iMac' started by tweek, Mar 5, 2020.

  1. tweek

    tweek Well-Known Member

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    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...
     
  2. tweek

    tweek Well-Known Member

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    Somewhat related PCIe 6.0 specification will allow for SSDs that have a sequential read/write of ~8GB/s (x1), ~16GB/s (x2) or even ~32GB/s (x4) by 2024/2025.

    By comparison all currently sold Macs are on PCIe 3.0 and has SSDs that have a throughput of ~3GB/s.

    Just in time for my upgrading my 2013 iMac.
     

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