Looking forward to breaking past 550MB/sec SATA3 SSDs, using PCIe, PCI NGFF (M.2), and software caching

Posted by Paul Braren on Jul 23 2013 in
  • Laptop
  • Storage
  • Above photo courtesy of "The SSD Review" from the excellent article here. Excellent diagram below from here.


    When I got my ThinkPad W520 back in October 2011, I noticed that the mSATA form factor was limited to SATA2's 3Gbit/sec speeds, on that particular early mSATA implementation. The slowdown my Runcore mSATA SSD experienced was noticeable, especially when compared to the speed obtained when booting from the same SSD installed in the same laptop's 2.5" drive bay, using an mSATA to SATA3 adapter.

    Flash forward to today (see what I did there?), and you'll notice that mSATA is available at SATA3 speeds on a few newer laptops, but we're still stuck at at the SATA3 spec's 6Gbit/sec limitation. This means about 550MB/sec maximum throughput. We've bumped up against an interface bottleneck, despite the faster speeds the latest SSDs are quite capable of delivering.

    When you think about laptops, desktops, and servers, wouldn't you rather bypass the old SATA interface entirely, and get that solid state goodness mounted right on the PCI bus? Well, that's the route the recent Haswell-based Apple Macbook Air has done, explained here. It uses a variant of NGFF (Next Generation Form Factor), aka M.2, a spec that was discussed at Anandtech back in September 2012 here, excerpt below.

    We've seen a bunch of custom SSD form factors with the arrival of Ultrabooks as well as systems like the MacBook Air and Retina MacBook Pro. The need is simple: standard 7mm or 9.5mm SSDs are too big for some of these machines, and you don't actually need all of that volume to build a fast drive. mSATA cards work as a small form factor solution but they are only available in a single size. We need flexibility both on length (to allow for higher capacities) as well as on the interface side to enable higher performance. The NGFF specification gives us just that.

    With the arrival of fast Samsung 840 EVO 128 to 1TB SSDs in traditional 2.5" SATA packaging, and a new line of fast PCIe 3.0 SSDs for desktops and servers, capacities and speeds are most certainly moving forward. There's also the promising Samsung RAPID Mode Windows software that essentially sets aside 1GB of even faster system RAM, to help cache your frequently accessed SSD data, with some ways of making those cached hotspots persist through reboots, described in the video below.

    It's tantalizing to begin to imagine what kind of speeds AND capacity NGFF will allow for in tiny Ultrabooks. It's looking likely we'll get to find out soon, with the wave of Haswell based Ultrabooks arriving with Windows 8.1 later this year. All these recent developments sure have me thinking about how to best go about obtaining the fastests SSDs at reasonable prices. Not just for family workstations, but perhaps for my home virtualization lab, to supplement its SSD cached RAID5 array and handful of SATA3 SSDs. Even further into the future, it'll be interesting to see what advances could happen in the world of SSD-based caching for hypervisors.

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