Wandering Thoughts archives

Faster SSDs matter to companies because they sell things

The computer hardware industry has a problem: systems mostly aren't getting (much) better any more, especially desktop PCs. The most famous example is that CPU performance has been changing only incrementally for years, especially for single threaded performance. This is a problem because a lot of hardware sales are upgrades and when there's no particular performance improvement you can trumpet people don't bother to upgrade. They do replace old machines eventually, but that's slower and less lucrative (and runs the risk of people leaking out to, eg, tablets and smartphones).

This is where a faster SSD interconnect matters to companies; it's a clear performance improvement they can point to. Whether or not it makes a difference in practice for most people, companies can trumpet 'much faster disk read and write speeds' as well as 'take full advantage of SSDs' and thereby move (more) hardware. No matter what it does in practice, it sounds good.

My general impression is that Intel and the motherboard companies are pretty desperate for things that will move new hardware, and really I can't blame them. So I wouldn't be surprised to see U.2 NVMe support appear in motherboards and systems quite fast, and I honestly hope it works to prop up their fortunes.

(As someone who is well out on the small tail end in terms of my PC hardware, I have a vested interest in a vibrant motherboard market that caters to even relatively weird interests like mine.)

Sidebar: the 'pushing technology' view

On a longer and larger scale view, drastically increased 'disk' access speeds that are essentially specific to SSDs also increase the chances that people will start building filesystems and other things that are specifically designed and tuned for SSDs, or just generally for things that look more like memory than rotating magnetic medium. It's been very useful to be able to pretend SSDs are hard drives, but they aren't really and we may find that systems are quite different and better when we can stop pretending.

(This too is likely to sell new hardware over the long term.)

The next (or coming) way to connect SSDs to your system

Modern SSDs have a problem: flash chips are so fast that they outpace even high speed SATA and SAS links. In the enterprise market the workaround for this is SSD 'drives' that are PCIe cards, but this has all sorts of drawbacks as a general solution. Since the companies involved here are not stupid, they've known this for some time and have come up with a new interconnection system, NVMe aka NVM Express.

The Wikipedia page is a bit confusing to outsiders, but as far as I can tell NVMe is essentially a standard for how PCIe SSDs should present themselves to the host system. NVMe devices advertise that they have a specific PCI device class and promise to have a common set of registers, control operations, and so on; as a result, any NVMe device can be driven by a single common driver instead of each company's devices needing their own driver.

(Most PCI and PCIe devices need specific drivers because there's no standard for how they're controlled; each different device has its own unique collection of registers, operations, and so on. This gives us, eg, a zillion different PCI(e) Ethernet device drivers.)

If this was all that NVMe was, it would be kind of boring because it would be restricted to actual PCIe card SSDs and those are never going to be really popular. But NVMe also has a physical standard called U.2 that lets you pull PCIe out over a cable to a conventional-ish SSD drive. This means that you can have a 2.5" form factor SSD mounted somewhere and cabled up that is an NVMe drive and thus is actually a PCIe device on one of your PCIe busses. Assuming everything works and U.2 ports appear in sufficient quantity on motherboards, this seems likely to compete with SATA for connecting SSDs in general, not just in expensive enterprise setups.

(U.2 used to be called SFF-8639 until this month. As you can tell, the ink is barely dry on much of this stuff.)

If I'm reading the tea leaves right, U.2 is somewhat less convenient than ordinary SATA because it requires cables and connectors that are a bit more than twice as big. This is going to impact port density and wiring density, but there are plenty of ordinary machines which have enough motherboard real estate and enough space for cables that this probably isn't a big concern. On the other hand I do expect a bunch of small motherboard and high density servers to deliberately stay with SATA or SAS for the higher achievable port density.

(PCIe and thus NVMe can also be connected up with a less popular connector standard called M.2. This is apparently intended for plugging bare-board SSDs directly into your motherboard instead of cabling things to mounts elsewhere, although I've read some things suggestion it can be coerced into working with cables.)

Does this all matter to ordinary people balancing the SSD inflection point? Maybe. My view is that it does matter in the long term for computer hardware companies, but that's going to take another entry to explain.

Thinking about people's SSD inflection points in general

What I'm calling the (or a) SSD inflection point is the point where SSDs get big enough and cheap enough for people to switch from spinning rust to SSDs. Of course this is already happening for some people some of the time, so the real question is when it's going to happen for lots of people.

(Well, my real question is when it's going to happen for me, but that's another entry.)

I don't have any answers. I don't even have any particular guesses or opinions. What I do have is an obvious observation.

For most people and most systems, the choice of HDs versus SSDs is not about absolute performance (which clearly goes to SSDs today) or absolute space (which is still by far in the hands of HDs both in terms of price per GB and how much TB you can get in N drives). Instead, unsurprisingly, it is about getting enough space and then if possible making it go faster. People can and do make tradeoffs there based on their feelings about the relative importance of more space and more speed, including ones that make their systems more complicated (like having a small, affordable SSD for speed while offloading much of your data to a slow(er) but big HD). This makes the inflection point complicated and thus the migration from HDs to SSDs is probably going to be a drawn out affair.

We've already seen one broad inflection point happen here, in good laptops; big enough SSDs have mostly displaced HDs, even though people may not have all the space they want. I doubt many laptop users would trade back, even if they have to carefully manage disk space on their laptop SSD.

My suspicion is that the next inflection point will hit when affordable SSDs become big enough to hold all of the data a typical person puts on their computer; at that point you can give people much faster computers without them really noticing any drawbacks. But I don't have any idea how much space that is today; a TB? A couple of TB? Less than a TB for many people?

(My impression is that for many people the major space consumer on home machines is computer games. I'm probably out of touch on this.)