Performance Consistency

Performance consistency tells us a lot about the architecture of these SSDs and how they handle internal fragmentation. The reason we do not have consistent IO latency with SSDs is because inevitably all controllers have to do some amount of defragmentation or garbage collection in order to continue operating at high speeds. When and how an SSD decides to run its defrag or cleanup routines directly impacts the user experience as inconsistent performance results in application slowdowns.

To test IO consistency, we fill a secure erased SSD with sequential data to ensure that all user accessible LBAs (Logical Block Addresses) have data associated with them. Next we kick off a 4KB random write workload across all LBAs at a queue depth of 32 using incompressible data. The test is run for just over half an hour and we record instantaneous IOPS every second.

We are also testing drives with added over-provisioning by limiting the LBA range. This gives us a look into the drive’s behavior with varying levels of empty space, which is frankly a more realistic approach for client workloads.

Each of the three graphs has its own purpose. The first one is of the whole duration of the test in log scale. The second and third one zoom into the beginning of steady-state operation (t=1400s) but on different scales: the second one uses log scale for easy comparison whereas the third one uses linear scale for better visualization of differences between drives. Click the dropdown selections below each graph to switch the source data.

For more detailed description of the test and why performance consistency matters, read our original Intel SSD DC S3700 article.

Samsung SSD 850 EVO 250GB
25% Over-Provisioning

The 850 EVO presents a healthy increase in IO consistency. The 840 EVO wasn't exactly inconsistent in the first place, but the 850 EVO takes the steady-state IOPS from ~3,000-5,000 IOPS to 5,000-8,000 IOPS, which is actually nearly on par with the 850 Pro. The 850 EVO has without a doubt one of the highest performance consistencies out of the value/mainstream drives we have tested.

Samsung SSD 850 EVO 250GB
25% Over-Provisioning


Samsung SSD 850 EVO 250GB
25% Over-Provisioning

TRIM Validation

To test TRIM, I filled a 120GB 850 EVO with sequential 128KB data and proceeded with a 30-minute random 4KB write (QD32) workload to put the drive into steady-state. After that I TRIM'ed the drive by issuing a quick format in Windows and ran HD Tach to produce the graph below.

And TRIM works as expected.

Endurance: Close to Planar MLC NAND AnandTech Storage Bench 2013


View All Comments

  • Kristian Vättö - Thursday, December 11, 2014 - link

    Hi Simon,

    Sorry for taking a while to respond -- I had to focus on my finals after I got the review done, so I couldn't catch up with all the comments until now.

    The 850 EVO is still a SATA 6Gbps design, so there won't be a SATA Express version of it. There may (and likely will) be an M.2 version coming, although that would also be limited to SATA 6Gbps since M.2 can support both SATA and PCIe interfaces. As for the form factors and capacities, it's impossible to say for sure but technically the 2242 form factor could max out at 512GB and the 2280 at 2TB (assuming double-sided PCB and 16x128Gbit dies per package).

    However, the SM951/PM951 will be available sometime next year, although it will be limited to OEM channels again (RamCity saves you, again). That's the PCIe 3.0 x4 NVMe M.2 drive with 3D NAND (SM=MLC, PM=TLC). I don't have any further details at this point, unfortunately.

    Regarding other PCIe SSDs, I should know more after CES when I meet with all the companies again and get an update on their schedules, but for now it looks like most designs are aiming at mid-2015 launch.
  • akula2 - Wednesday, December 10, 2014 - link

    850 Pros are my last Samsung SSD products to buy. For the upcoming X99 extreme workstations, I'll to go with:

    1) SanDisk Extreme Pro 960GB (today $490 vs $600 of 850 Pro). The performance of both SSDs are comparable.
    2) Mushkin Scorpion Deluxe 960GB PCI-E SSD: this one decimates all the best SSDs.
    3) Intel SSD DC P3700 800GB and 1.6TB models: The King
  • HisDivineOrder - Wednesday, December 10, 2014 - link

    This is the problem with Samsung. When they first came into the market, they blew the competition away with incredible performance, reliability, and pricing.

    The 840 came with TLC, promising superior pricing with good performance, but in fact pricing was out of whack, putting it way above the 830 that had just left the market. Then 840 Pro took over the high end where only fools dare to tread.

    The 850 line (Pro and EVO) raise the prices even higher. It's like Samsung thinks they're the Apple of SSD's and can do whatever they want in pricing. To hell with the competition, people will pay whatever they say.

    It's a shame. Way back, I got an 830 because it was a great value. This time around? I waited until Black Friday and picked up a Sandisk after waiting a couple of years for Samsung to remove their head from out of their butt. My 480GB Extreme Pro only cost me $185 and it will last me a good long while.

    That could have been you, Samsung. I didn't want to put another brand SSD in my machine. I wanted to have only one Samsung Magician. But Samsung pricing is completely absurd.

    So, eh, bye bye, Samsung.
  • Supercell99 - Sunday, December 14, 2014 - link

    They acting like Intel with does Xeon chips, except, Samsung actually has other competition with SSD's. Like you, with my next SSD purchase, I will have to look at other companies as Samsung's $/GB vs the competition has continued to get worse. Reply
  • philipma1957 - Thursday, December 11, 2014 - link

    I would like a 1.2th ssd that is really 1.5tb with extra provisioning.
    I would like it to have good 4k random read writes more then anything.

    I have 2 1tb ssds and use them for mac minis.

    I use external thunderbolt drives and boot with the 1 tb ssd's the drive in the mini is merely a back up for me. I find I could use a little bigger then 1tb for the video recording I do. Still waiting for a bigger ssd.
  • harrynsally - Saturday, December 27, 2014 - link

    Didn't take long for the MSRP to drop. Was on sale at Newegg and I just bought a 250GB 850 EVO for $114 shipped.

    Although I previously, purchased two Crucial 256GB MX100s, to use in a couple of older laptops, which installed and continue to run flawlessly, wanted to upgrade the HDD in a new laptop.

    Was really conflicted in not buying another MX100, but the better performance specification and 5 year warranty won out.
  • rvb - Monday, January 19, 2015 - link

    Has anyone seen info for the write-block and erase-block sizes for the 1TB 850 Pro? I am intending to RAID 4 of them together, and I want to make sure that my RAID's stride-size is a multiple of the larger of those two values. If they are both something small like 4KiB, then pretty much any larger Pow2 value I choose will be fine. But my only other SSD purchase (OCZ Vertex 4) had a WBS of 8KiB and an EBS of 2MiB. In that case, if I'm going to be writing large files to my RAID, then I think it's useful to know that the EBS is so large, so that I can set my RAID stride-size accordingly.
    Samsung's "data sheet" for the 850 Pro series neglects to give this information... however, I do note that they only quote random-write performance in terms of 4KB transfers, which may imply that at least their WBS is 4KiB. I just wish I knew for certain, and also the EBS ?
  • mirkogutic - Saturday, January 24, 2015 - link

    Hi, i own 2 of the 120GB Samsung EVO 850.
    Should I put them in RAID 0 or leave them as separate drives?
    It seems that Samsung Magician works only when drives are not in RAID mode.
    Also, RAPID mode works only on one drive and when not in RAID.
  • Nilth - Thursday, April 16, 2015 - link

    Sorry for the probably dumb question, but isn't the way turbowrite works detrimental for the ssd longevity? If I understood correctly, (almost) ALL the writes are going to pass through the same "x" GB slc buffer. Isn't that partition going to "wear out" son enough? Reply
  • djdownfawl - Thursday, June 4, 2015 - link

    @Kristian Vättö
    As of today's prices Samsung 850 EVO vs the PRO. Would you recommend buying the EVO or the PRO?

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