It's not news that full speed NVMe disks are extremely fast, as well as extremely good at random IO and doing a lot of IO at once. In fact they have performance characteristics that upset general assumptions about how you might want to design systems, at least for reading data from disk (for example, you want to generate a lot of simultaneous outstanding requests, either explicitly in your program or implicitly through the operating system). I'm not sure how much write bandwidth normal NVMe drives can really deliver for sustained write IO, but I believe that they can absorb very high write rates for a short period as you flush out a few hundred megabytes or more. This is a fairly big sea change from even SATA SSDs (and I believe SAS SSDs), never mind HDDs.
About a decade ago, I speculated that everyone was going to be forced to migrate to SATA SSDs because developers would build programs that required SATA SSD performance . It's quite common for developers to build programs and systems that run well on their hardware (whether that's laptops, desktops, or servers, cloud or otherwise), and developers often use the latest and best. These days, that's going to have NVMe SSDs, and so it wouldn't be surprising if developers increasingly developed for full NVMe performance. Some of this may be inadvertent, in that the developer doesn't realize what the performance impact of their choices are on systems with less speedy storage. Some of this will likely be deliberate, as developers choose to optimize for NVMe performance or even develop systems that only work well with that level of performance.
This is a potential problem because there are a number of ways to not have that level of NVMe performance. Most obviously, you can simply not have NVMe drives; instead you may be using SATA SSDs (as we mostly are, including in our fileservers ), or even HDDs (as we are in our Prometheus metrics server ). Less obviously, you may have NVMe drives but be driving them in ways that don't give you the full NVMe bandwidth. For instance, you might have a bunch of NVMe drives behind a 'tri-mode' HBA , or have (some of) your NVMe drives hanging off the chipset with shared PCIe lanes to the CPU, or have to drive some of your NVMe drives with fewer than x4 PCIe because of limits on slots or lanes.
(Dedicated NVMe focused storage servers will be able to support lots of NVMe devices at full speed, but such storage servers are likely to be expensive. People will inevitably build systems with lower end setups, us included, and I believe that basic 1U servers are still mostly SATA/SAS based.)
One possible reason for optimism is that in today's operating systems, it can take careful system design and unusual programming patterns to really push NVMe disks to high performance levels. This may make it less likely that software accidentally winds up being written so it only performs well on NVMe disks; if it happens, it will be deliberate and the project will probably tell you about it. This is somewhat unlike the SSD/HDD situation a decade ago, where the difference in (random) IO operations per second was both massive and easily achieved.
(This entry was sparked in part by reading this article ( via ), which I'm not taking a position on.)