When it comes to flash capacity, more is better. The question is whether two are better than one. Today, we look at the Samsung 950 Pro 256GB SSD again, but with a focus on pairing two drives in a RAID 0 array. This option costs a little more than a single Samsung 950 Pro 512GB, but does the array offer a performance advantage that makes up the price difference?
Non-volatile Memory Express (NVMe) is a new storage protocol designed to reduce latency in the software stack for flash and next-generation solid-state media. There are only two viable client-flash processors available in the M.2 form-factor: the Samsung UBX and the Toshiba TC58NCP0706SB (found in the Toshiba XG3 and the upcoming OCZ Storage Solution's RevoDrive 400).
The Samsung UBX flash processor has been on the market for nearly a year now. It first appeared in the SM951-AHCI and later came to market with NVMe in the SM951-NVMe and PM953, both OEM products sold to system builders. Samsung eventually brought the UBX controller to the retail market in the 950 Pro, and it is one of the best-performing SSDs available today.
Samsung released the 950 Pro in only two capacity sizes—256GB and 512GB. The company claimed a 1TB model would follow the initial release in early 2016 but that drive has yet to appear. In our first review of the 950 Pro, we tested three configurations with a single 256GB, a single 512GB and two 512GB drives in a RAID 0 array. We didn't have access to a second 950 Pro 256GB drive to obtain RAID numbers during the test, but that changed last week when Samsung shipped us a full retail 256GB drive to round out our coverage.
The 950 Pro 256GB compares well to the larger 512GB model, but there are some key differences in performance and endurance. That starts with the 300 MB/s sequential read difference that favors the larger drive. The 950 Pro 256GB takes an even larger cut with sequential write speed, a 600 MB/s loss. The 256GB model also has half the endurance, but that's to be expected given the low number of NAND die Samsung needs to reach these capacities.
Random performance is also slightly different. The same can be said about the power consumption.
The 950 Pro uses Samsung's UBX PCIe 3.0 x4 to flash controller. The UBX was configured to support the NVMe protocol, which reduces latency and allows random performance to increase due to greater parallelism. The NVMe-enabled controller is paired with Samsung's 32-layer V-NAND and a single 512MB DRAM buffer used to cache map data.
Pricing, Warranty And Accessories
The 950 Pro 256GB currently sells for as low as $190, while the 512 GB sells for $330. Two 950 Pro 256GB drives cost about $50 more than the single, larger-capacity drive. Today we'll see if the performance of two drives makes up the difference.
The 950 Pro products ship as bare drives but Samsung allows users to download two useful software packages. The first is Magician, an SSD toolbox that allows users to monitor the status of Samsung SSDs, optimize operating system conditions, and perform some disk-management operations. Samsung also has a custom data-migration tool that allows users to clone data from an existing drive and transfer to your new Samsung drive.
A Closer Look
Not much has changed with the 950 Pro since we first tested them other than the final sticker on the drive itself. For comparison, there is an image of the NDA-release sample and the final retail sample together.