Congratulations, OCZ. You can come out of hiding now—no longer are you defined by the bargain-basement Trion line and Toshiba TLC NAND. The RD400 signals that all is again as it should be in OCZ-land. This M.2 PCIe-NVMe SSD reaches a read speed of 2.1GBps, meaning the company is once again shipping products that pursue the limits of performance. Thank goodness.
M.2 SSD variations
M.2 SSDs span three distinct types: SATA, PCIe-AHCI, and PCIe-NVMe. The first uses the SATA bus that some M.2 sockets implement, and is no faster than 2.5-inch SATA SSDs. The advantages are small size and convenience. The other two types use M.2’s PCIe channels (not all M.2 slots have them) and vary only in the transport protocol: the older AHCI, or the newer NVMe. (The RD400, as mentioned earlier, uses NVMe.) In most designs to date, AHCI can hang with NVMe when writing, at around 1.2GBps, but NVMe is far faster at reading. You’ll usually get 2GBps or more with NVMe compared to AHCI’s range of 1.1GBps to 1.4GBps.
Note that even if your M.2 slot supports PCIe, your motherboard’s BIOS must support NVMe to boot from an M.2 PCIe-NVMe drive. Most performance motherboards have been upgraded for this, but many mainstream models have not. Older PCIe-AHCI M.2 drives are far more likely to be hassle-free boot drives.
Testing and performance
The RD400 tested just a tad slower than its rival, the Samsung 950 Pro, in AS SSD’s sequential tests. It read at about the same 2.1GBps, but was some 200MBps off the pace writing. That may sound like a lot, because the dip from 1.4GBps to 1.2GBps is almost a 15 percent drop-off. But at those speeds, the difference is subjectively unnoticeable.
In the 4K threaded tests, the RD400’s results were the inverse of the 950 Pro’s. OCZ’s new drive nearly doubled the 950 Pro’s writing, but fell well short of its rival’s read speed. If you’re running an application that scattershots small writes, then the RD400 might be the better choice. For applications that read from multiple files simultaneously, then the 950 Pro will be what you want. However, threaded file writing is so new to the game that few applications are designed to take advantage of it.
Note also that this review’s results were obtained using a beta driver, as we did our testing prior to the product’s launch.
The RD400 is quite a bit faster than M.2 PCIe drives from previous generations, like the PCIe-NVMe Samsung SM951, as well as PCIe-AHCI drives like the Samsung XP941 and Kingston’s HyperX Predator.
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