Results: Sequential Performance
Fantastic sequential read and write performance is a trademark of modern SSDs. To measure it, we use incompressible data over a 16 GB LBA space, then test at queue depths from one to 16. We're reporting these numbers in binary (where 1 KB equals 1024) instead of decimal numbers (where 1 KB is 1000 bytes). When necessary, we're also limiting the scale of the chart to enhance readability.
128 KB Sequential Read
Really, this is where SanDisk's A110 kicks things into high gear. Perhaps I'm giving away the plot a little early, but in most regards, SanDisk's upcoming drive is comparable to the SATA-based SSDs we know so well. That is, except when it comes to sequential performance. The SATA 6Gb/s contenders max out right above 500 MB/s, while the A110 hits its afterburners and flies right by (up to a blazing 750 MB/s). In truth, it's probable that many existing SSDs would do the same if it wasn't for SATA's pesky 6 Gb/s ceiling.
128 KB Sequential Write
We see the story being told in our sequential write performance metric. With the throughput of two PCI Express 2.0 lanes available to it, the A110 pushes past 600 MB/s. Marvell's controller is clearly able to exceed the previously-imposed 6 Gb/s limit, though lower-capacity drives likely won't be able to repeat the performance of this 256 GB sample, since write speed is affected by the number of physical NAND devices present.
Here's a break-down of the maximum observed 128 KB sequential read and write performance with Iometer:
It's not surprising to see SanDisk's A110 at the head of the pack. Is it fair to even include the A110? Absolutely. We're looking at the next-generation storage form factor, after all. There's something else all of these drives share in common: they all leverage AHCI, which, ironically, isn't optimized for solid-state storage. This interface allowed hard drives to asynchronously stack I/O requests for better performance. The benefit over IDE was clear, but there's still a lot more than can be done with SSDs. That'll change with NVMe.
Technically, the P320h we reviewed in Micron RealSSD P320h Review: A PCIe Drive Capable Of 3.2 GB/s uses IDT's 32-channel PCIe NVMe-capable controller over an eight-lane PCI Express 2.0 interface. Micron uses its own proprietary driver though, meaning it isn't really NVMe. In a real NVMe-enabled ecosystem, you won't need a special driver package. When the time comes, NVMe will help facilitate tremendous performance improvements through a re-imagining of the way I/O is handled by the operating system.
