Samsung 950 PRO SSD RAID-0 Performance Tests
By David Ramsey
Full Disclosure: Samsung provided the product samples used in this article.
Samsung’s 950 PRO m.2 PCI-E SSD set new performance records for a consumer SSD, blasting through the limits of SSDs tethered to the old SATA interface. What could be better than one of these blazing-fast solid state storage monsters? Two of them in RAID-0! In this article, Benchmark Reviews explores the outer limits of storage performance with a pair of 512GB Samsung 950 PRO SSDs on our MSI Z170A Gaming M7 test system.
We’re excited to be able to being you this test, and thank Samsung for providing us with the two 950 PRO SSDs that allow us to do so.
Disk Interface Bandwidth
When Serial ATA (SATA) replaced the old IDE/ATA disk interface standard, it brought much greater performance potential as well as much smaller cables. With SATA Revision 3 (also known as “SATA 6”), the raw data rate increased to 6Gb/s. With standard 8/10 disk data encoding, this translates into a maximum theoretical bandwidth of 600MB/s. This is far more than any hard disk can achieve, but consumer-level SATA SSDs have started bumping up against this limit, returning real-world speeds over 560MB/s.
But the flash NAND memory used in modern SSDs is capable of much, much greater speeds: all it needs it a way to transfer the data that can handle more bits per second. The PCI Express (PCI-E) lanes of modern computers provide a perfect solution. A single PCI-E 2.0 lane can transfer 500MB/s, while a single PCI-E 3.0 lane almost doubles that to about 985MB/s. The Samsung 950 PRO m.2 SSD can use up to four PCI-E 3.0 lanes (it’ll work with fewer lanes, although performance will be limited) giving a theoretical maximum throughput of a staggering 4GB/s. In our test of a single Samsung 950 PRO m.2 SSD on our MSI Z170A Gaming M7 motherboard, we saw a maximum sustained read speed of 2.3GB/s in AIDA64, and up to 2.6GB/s in the ATTO disk benchmark.
PCI-E Lane Availability
Of course, getting this performance depends on having both the PCI-E lanes available, and the m.2 slots (or an m.2 PCI-E adapter card such as Silverstone’s ECM20). Prior to the recent introduction of Intel’s Z170 Express chipset, most consumer systems were limited to 24 PCI-E lanes: 16 3.0 lanes from the processor and 8 2.0 lanes from the chipset. An enthusiast system’s hardware– graphics cards, USB 3.0 ports, etc.– could easily use all the available PCI-E lanes; in fact, some motherboards even had physical switches allowing you designate how the available lanes were allocated. Some motherboards added expensive PCI-E multiplexer chips to try to spread the available lanes across more devices.
The X99 LGA2011 platform has up to 40 PCI-E 3.0 lanes available (the exact number depends on which CPU you use), but it’s expensive and doesn’t natively support m.2.
Enthusiast salvation arrived late last year with the Intel Z170 chipset, which provides 20 PCI-E 3.0 lanes on its own; combined with the 16 lanes from the processor, 36 lanes are available. Along with native m.2 support, this opens up a slew of possibilities…like, say, dual m.2 RAID!
SATA’s not going down without a fight: the SATA Revision 3.2 specification defines a PCI-E interface for SATA, as well as the traditional interface. Known as “SATA Express”, it’s supported by additional connectors on most Z170 motherboards, such as these on our MSI Z170A Gaming M7 test platform:
Using up to two PCI-E lanes per drive, SATA Express attempts to bridge SATA and PCI-E, and while it’s a noble attempt, it simply hasn’t caught on with SSD vendors. Although a few vendors announced SATA Express SSDs, I’ve never seen one, and can’t find any for sale on Newegg or Amazon.
I’m not a big fan of the m.2 form factor: small, bare circuit boards are vulnerable to physical damage and static discharge, and the tiny, fiddly screws and posts needed to mount an m.2 drive are clumsy to deal with. Still, it looks as if m.2 will be the way for SSDs to move to the next performance level.