An M.2 SSD in name only
The future of performance solid-state drive storage lies with the PCIe interface. Set to usher in a new era of superfast SSDs, the M.2 storage interface is shovelling huge amounts of data down speedy PCIe lanes. And we’re starting to see the green shoots of its continued development right now. More and more manufacturers have started to release M.2 drives, with the socket appearing in many new laptops and mainstream motherboards.
There’s also the tantalising prospect of the Non-Volatile Media Express protocol (NVMe) replacing the current AHCI setup, itself hobbling even the fastest PCIe SSDs with its many mechanical legacy hoops that SSDs still need to jump through. On top of that, thanks to Samsung’s latest range of consumer drives, we’re also getting 3D NAND Flash memory to sort out the storage density and longevity issues we’ve been suffering with.
So Samsung releases an M.2 850 EVO – the very drive range with its vertical, or V-NAND, memory – and we get all excited. Could this be the holy trinity of SSD advancement, a solid-state drive with 3D stacked memory, operating on the latest M.2 PCIe interface with the new NVMe protocol? Would that it were, dear reader. Would that it were…
We can discount NVMe immediately. That much vaunted SSD-specific protocol is still a while away from landing in our desktops. But we’ve still got an M.2 drive, right? Well, this is where things get really frustrating. Yes, the 850 EVO M.2 has been designed in that form factor, but it’s using a little-known component of the M.2 interface – SATA. As well as providing a connection to the PCIe lanes of a motherboard, and support for both the AHCI and NVMe protocols, M.2 can also provide legacy support, plumbing directly into the SATA interface.
What we have here then is an M.2 drive that’s unable to actually take advantage of this new interface properly at all. It doesn’t matter if you plug it into a x2 or x4 slot, it will still just route everything straight through to SATA, suffering all the bandwidth limitations that the aging interface offers. Samsung is claiming this drive is designed for the consumer market, for those looking for a decent SSD upgrade for their M.2-sporting thin ‘n’ light notebooks. That’s especially frustrating considering Samsung is still refusing to release its speedy XP941 or upcoming XP951 M.2 drives to the consumer market despite this tacit acknowledgement that consumers are ready to mess about with bare PCBs in their notebooks.
What’s also tricky is that support for this bizarre subset of the M.2 interface is very limited when it comes to desktop motherboards. We went through all the Asus boards we have in the office with M.2 interfaces – and a PCIe expansion board too – and none supported it. Thankfully our ASRock X99X Killer Fatal1ty did, otherwise we wouldn’t have got to be underwhelmed by the 850 EVO M.2’s performance at all. At least not first-hand.
And underwhelming is definitely the word. If it were performing at the same level as the 2.5-inch drive that would still be mildly disappointing for an M.2 form factor but, considering its SATA limitations, not surprising. That, however, is not the case. Sequential read and write performance is on a par with what the 2.5-inch version can manage, namely sitting around the 500MB/s mark characterising most current-gen SSDs, but the random 4K performance is well off the pace.
The standard drive hits 36MB/s and 108MB/s respectively – about as fast as 4K performance gets right now – but this M.2 SATA version can only manage 22MB/s and 62MB/s. Those numbers are far from awful, but lag significantly behind the bargain £150 MX100 512GB drive. It’s the same story for our real-world tests too, where it’s half a minute behind its 2.5-inch sibling when it comes to our large Steam folder transfer. That’s an enormous difference in performance.
We understand Samsung wants this to be an affordable drive for the thin ‘n’ light upgrade market, but releasing an M.2 drive without the expected performance benefits just seems odd. Especially when it plain refuses to properly release its super-quick XP941 to the public. So we’re struggling to see why anyone would want this drive for their machine long-term – and by the looks of it cutting the 850 EVO’s five-year warranty down to just three years for the M.2 version, Samsung’s struggling too. – Dave James
Specifications
Capacity - 500GB
Form factor - M.2 2280
Interface - SATA 6Gbps
Memory controller - Samsung MGX
Memory type - Samsung 40nm 3-bit MLC V-NAND
Cache - 512GB LPDDR3