The Samsung SSD 850 EVO mSATA/M.2 Review
by Kristian Vättö on March 31, 2015 10:00 AM ESTSequential Read Performance
Our sequential tests are conducted in the same manner as our random IO tests. Each queue depth is tested for three minutes without any idle time in between the tests and the IOs are 4K aligned similar to what you would experience in a typical desktop OS.
In sequential read performance the difference between drives is rather marginal, but in power consumption we start to see some differences. At 250GB and 120GB the 850 EVO is very efficient, but the 500GB and 1TB are again more power hungry.
Looking at performance across all queue depths doesn't reveal any surprises: at QD2 and higher all drives are practically saturating the SATA 6Gbps interface. What's notable, though, is that the 1TB degrades in performance as the queue depth increases. I wonder if this is a thermal issue (mSATA/M.2 don't have a chassis to use as a heatsink) or just poor firmware optimization.
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Sequential Write Performance
Sequential write testing differs from random testing in the sense that the LBA span is not limited. That's because sequential IOs don't fragment the drive, so the performance will be at its peak regardless.
In sequential write speed the capacity plays a more significant role because the 120GB and 250GB are noticeably behind the 500GB and other higher capacity drives. The poor performance of the 1TB model is once again a surprise, though.
The full graph of all queue depths shows the reason for the 1TB's low performance: it starts high at ~430MB/s, but after that the performance decreases.
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Flunk - Tuesday, March 31, 2015 - link
This is what makes M.2 such an annoying standard. They tried to accommodate everything and ended up with compromises that don't make sense and will probably be written out of the standard in a future version.setzer - Tuesday, March 31, 2015 - link
Also don't forget about the single and double sided thing as noted in the article there are some laptops that only accept single-sided.Also there is nothing to prevent a manafucturer to put a B+M keyed M.2 socket but only connect the USB traces. See toshiba's Z30's laptops for a pratical example.
The joys of M.2 are great :P
ilkhan - Wednesday, April 1, 2015 - link
Answer: Ports should be wired and keyed for sata and pci-e.devices can be whatever they need.
The keys are there to prevent a pci-e device in a sata host.
rtho782 - Tuesday, March 31, 2015 - link
I still don't see a reason to replace my ageing 256GB Samsung 830s in RAID 0.I really want a decent PCIe NVMe M.2 or SATAe SSD of about 500GB, preferably Samsung and 3D nand. But nothing :(
MrCommunistGen - Tuesday, March 31, 2015 - link
Looks like the 500GB model is the performance sweet spot.I'm not that surprised with the different performance profile on the 1TB model since it is using the older MEX controller. Could the 1TB's stuttering under steady state load be due to thermal throttling of the controller?
I was not expecting the smaller capacity drives, particularly the 120GB model to have such (relatively) low performance. Still, compared to drives of yesteryear, performance is still quite good. My HTPC has an old 96GB Kingston V+100 but still feels pretty snappy. I'm sure that even the 120GB 850 Evo would run circles around that drive - and as such have plenty of performance for an average user.
sonicmerlin - Friday, April 3, 2015 - link
Ha I have that exact same Kingston drive in my desktop. I can only install like 1 or 2 games at once, but it's totally worth it. I doubt any SSD upgrades would make my computer feel even faster than it already is.Mrduder11 - Tuesday, March 31, 2015 - link
I can't remeber where I read it but should we be concerned about these drives getting too hot where it affects performance?Mecharon1 - Tuesday, March 31, 2015 - link
Is this drive bootable? More specifically, can I install my OS on the 120GB M.2 version and use something else for bulk storage?foxtrot1_1 - Tuesday, March 31, 2015 - link
That depends on the motherboard, but Windows 8.1 and Windows 10 should allow you to boot from M.2 no problem. Your BIOS is the issue.This is a golden age for PC hardware (at least, it will be this fall) but the proliferation of specifications and standards is really stupid. Get your act together, OEMs.
Kristian Vättö - Wednesday, April 1, 2015 - link
SATA is always bootable regardless of the form factor and OS, and the 850 EVO is a SATA drive (M.2 supports both SATA and PCIe). The bootability issue only applies to PCIe M.2 drives.