The Samsung SSD 850 EVO mSATA/M.2 Review
by Kristian Vättö on March 31, 2015 10:00 AM ESTMixed Random Read/Write Performance
Mixed read/write tests are also a new addition to our test suite. In real world applications a significant portion of workloads are mixed, meaning that there are both read and write IOs. Our Storage Bench benchmarks already illustrate mixed workloads by being based on actual real world IO traces, but until now we haven't had a proper synthetic way to measure mixed performance.
The benchmark is divided into two tests. The first one tests mixed performance with 4KB random IOs at six different read/write distributions starting at 100% reads and adding 20% of writes in each phase. Because we are dealing with a mixed workload that contains reads, the drive is first filled with 128KB sequential data to ensure valid results. Similarly, because the IO pattern is random, I've limited the LBA span to 16GB to ensure that the results aren't affected by IO consistency. The queue depth of the 4KB random test is three.
Again, for the sake of readability, I provide both an average based bar graph as well as a line graph with the full data on it. The bar graph represents an average of all six read/write distribution data rates for quick comparison, whereas the line graph includes a separate data point for each tested distribution.
Mixed random performance appears to be brilliant and power consumption is moderate too.
The 850 EVO has a typical curve at 250GB and above where the performance more or less stays constant until hitting 100% writes where it jumps up considerably. Only the 850 Pro breaks this trend as its performance in fact decreases as the share of writes is increased.
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Mixed Sequential Read/Write Performance
The sequential mixed workload tests are also tested with a full drive, but I've not limited the LBA range as that's not needed with sequential data patterns. The queue depth for the tests is one.
In mixed sequential workload the 850 EVO is good, but not overwhelming.
The 850 EVO's "bathtub" curve is a bit different from others' in the sense that the drop in performance is smooth rather than being sudden right after adding reads/writes to the mix.
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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.