Just in time for the launch of Apple's newly redesigned Mac Pro tower, OWC has introduced the ‘fastest SSD [they've] ever built’, the Accelsior 4M2. The high-end solid state drive combines multiple M.2 drives to offer up to 8 TB of storage, with aggregate read/write well over 6000 MB/s.

The OWC Accelsior 4M2 SSD is essentially a PCIe x8 backplane based on the ASMedia ASM2824 PCIe 3.0 switch, which in turn is being used to drive a quartet of PCIe 3.0 x4 M.2 slots. The Accelsior then fills out these slots with four of OWC's Aura P12 M.2-2280 drives (Phison’s PS5012-E12 controller with SLC caching support, DRAM, & Toshiba’s 3D TLC NAND memory). To ensure consistent performance as well as to ensure reliability, the SSD is also equipped with a large heat spreader, as four Aura drives can produce a significant amount of heat.

When it comes to capacity, the Accelsior 4M2 storage solution will be available in 1 TB, 2 TB, 4 TB, and 8 TB raw capacities. OWC in turn rates the SSD for sequential read speeds up to 6318 MB/s, as well as sequential write speeds up to 6775 MB/s.

As is often the case for high-end OWC drives, the Accelsior 4M2 is meant to be used with OWC’s SoftRAID software, which supports various RAID modes (RAID 0, RAID 1, JBOD, etc.). Otherwise the drive can also be used in PCs – despite the Mac-focus, it's presented as a generic PCIe card – but PC users will need to supply their own RAID software.

The OWC Accelsior 4M2 SSDs
  1 TB
2 TB
4 TB
8 TB
Formatted Capacity 931 GiB 1863 GiB 3725 GiB 7451 GiB
Drives 4 × OWC Aura P12 M.2-2280 drives
Phison’s PS5012-E12 controller,
SLC caching support,
DRAM cache,
Toshiba’s 3D TLC NAND memory
(7% overprovisioning)
PCIe Switch ASMedia ASM2824
Internal RAID SoftRAID
Peak Read Speed 6318 MB/s
Peak Write Speed 6775 MB/s
Interface PCIe 3.0 x8
Power Bus powered
Form-Factor Full Height Half Length PCIe
Compatibility macOS 10.13 or later
Windows 10 or later
Warranty 5-year warranty
Price (MSRP) $479.99 $629.99 $949.99 $1,599.99

OWC will start shipments of the Accelsior 4M2 SSDs on the week of December 30th. The barebones card is priced at $249.99, the 1 TB version costs $479.99, whereas the top-of-the-range 8 TB model carries a $1,599.99 MSRP.

Related Reading:

Source: OWC

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  • MenhirMike - Monday, December 23, 2019 - link

    Curious why they use a PCIe Switch - does the Mac Pro not support bifurcation? The Xeon definitely has enough PCIe lanes, so using something like a $50 ASUS M.2 X16 card would be a cheaper option (and one that gives x16 instead of x8 speed), especially since the RAID is software-side anyway.

    That said, the price isn't bad for a card that uses a PCIe switch, I just question why you'd buy a card with a PCIe Switch if you don't have a lack of lanes available - the Cascade Lake Xeon W's have 64 PCIe 3.0 lanes across the board.
  • GreenReaper - Monday, December 23, 2019 - link

    The Mac Pro has one PCIe x16 slot, but two PCIe x8 slots: https://www.apple.com/uk/mac-pro/specs/
    Realistically, you probably won't be using 16x of bandwidth, so using the 8x slots is more efficient. It means you could use four cards at least at half capacity, which isn't possible with a 2 x 4x card.
  • MenhirMike - Monday, December 23, 2019 - link

    Yeah, but the x16 slot is in addition to the 2 x16 for Graphics cards if I read this correctly (2x MPX, which is 1x16 and 1x8, and then in addition 1x16 and 2x8, and then one x4 with Apple's IO card).

    So unless you have something else, there an x16 slot for four x4 drives. Of course, bifurcation would mean you have to use x16 for four drives, while a bridge allows sticking as many drives as you want into any PCIe slot. I'm not criticizing this product for existing, I'm just wondering why you'd opt for a Bridge if you have the slot free.
  • MenhirMike - Monday, December 23, 2019 - link

    To answer myself, the Apple Afterburner card is meant for that free x16 slot. That makes sense.
  • dontlistentome - Monday, December 23, 2019 - link

    All because it's in the CPU, doesn't mean Apple can be bothered to support it. eg - for displays, Displayport MST has been around for an age, but apple don't support it.
  • Kevin G - Thursday, December 26, 2019 - link

    The latest Mac Pros don't have enough PCIe lanes coming from the CPU, even if it is a respectable 64 lanes. Throwing the extra 24 from the PCH doesn't do much for this equation since that is bottlenecked by the DMI uplink. The main driving factor for the need of so many switches is Thunderbolt which gets fed four PCIe lanes per pair of ports.

    There is no guarantee that the slot this expansion card goes into has all 16 physical lanes routed to it. Thus to be able to guarantee usage of all four M.2 lots is that it has to sit behind a PCIe switch, even if it takes a performance hit due to the bandwidth reduction. (There is a sliver of hope for RAID1 writes as the PCIe switch might be able to duplicate the write command there instead of having it sent individual for each M.2 drive. This comes down to the specific PCIe switch used and software support.)

    The use of a switch also permits it to be used in the previous generation of Mac Pros that only have PCI 2.0 rated slots while allowing the full bandwidth of a single M.2 to be used. IE 4x PCIe 3.0 M.2 -> 8x PCIe 2.0 slot
  • boeush - Monday, December 23, 2019 - link

    Would be interesting to see actual real-world performance benchmarking on something like this, especially as compared to regular consumer/prosumer SSD drives (max storage capacity aside...)
  • SanX - Monday, December 23, 2019 - link

    6 gig per sec... And now let's return to the real world where formatted read/write in c/c++ is 2-3 ***megabytes*** per second, and in most Fortran 50-100. Unformatted I/O in C, Python etc faster but still 10 MB/s, in Fortran 100-300 MB/s. Only HDF and Silverfrost Fortran can reach 4 GB/s. Funny, even own tools of HDF groplups like H5dump converts H5 files to text with turtle speed 1/3000 of the power of this drive with 1/1000 for unformatted output. Hahahaha
  • Slash3 - Tuesday, December 24, 2019 - link

  • patmanRR - Tuesday, December 24, 2019 - link

    No, it is not 3mb/s.

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