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
Default
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
Default
25% Over-Provisioning

 

Samsung SSD 850 EVO 250GB
Default
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
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  • KAlmquist - Monday, December 8, 2014 - link

    My guess is that Samsung doesn't have the ability to produce very much V-NAND. So the 850 PRO, and now the 850 EVO, are priced to encourage most people to choose SSD's from the 840 line rather than the 850 line, preventing demand for the 850 line from exceeding the supply. Reply
  • rms141 - Monday, December 8, 2014 - link

    The absence of the Samsung 840 Pro from the Storage Bench 2013 section is pretty odd. Why wouldn't you include the previous generation's higher performing product? This is a little bit like publishing a GTX 970 review without including the GTX 780 for reference. Reply
  • Kristian Vättö - Tuesday, December 9, 2014 - link

    You can always use the Bench tool to compare any and all drives that we have tested over the years:

    http://www.anandtech.com/bench/SSD/65
    Reply
  • fokka - Monday, December 8, 2014 - link

    it doesn't make much sense to complain about the msrp when the drive is just now trickling to retailers. you're probably not gonna make a good deal on a 850 evo before christmas, but the prices will come down considerably in q1/q2 2015, they always do.

    that said, i wouldn't mind paying a couple bucks more for a 850, compared to a 840, since it's just the all around better drive and it's lower power consumption alone makes it the better option for laptops.

    pitted against an mx100 it might be a tougher sell, but let's just wait a bit for the prices to come down and give the early adopters some time to beta-test the firmware for us in the meantime.
    Reply
  • Morawka - Tuesday, December 9, 2014 - link

    Does TurboWrite, native encryption, and TRIM work in RAID 0 on the 850 EVO? Thats the only way i would invest $500+ into a SSD still bottlenecked by Sata 6 Reply
  • hojnikb - Tuesday, December 9, 2014 - link

    All of that should work with appropriate motherboard/storage drives, because drive itself is not aware whenever is in RAID or not. Reply
  • hojnikb - Tuesday, December 9, 2014 - link

    *drivers Reply
  • paesan - Tuesday, December 9, 2014 - link

    I just got a 1TB 840 evo for $369. No way the 850 evo is worth the extra $100. Reply
  • R3MF - Tuesday, December 9, 2014 - link

    How do you conduct this review of a perfomance oriented SSD without discussing:

    1. m.2 format (or lack thereof)?
    2. PCIe 3.0 4x m.2 performance (vs SATA 6G)?
    3. NVME m.2 performance (vs SATA 6G)?

    It is the end of 2014, who seriously spends £320 on a 1TB performance SSD without considering the high-speed m.2 drives just around the corner, to which a growing number of enthusiasts have empty slots on their shiny new motherboards?
    Reply
  • hojnikb - Tuesday, December 9, 2014 - link

    >How do you conduct this review of a perfomance oriented SSD without discussing:

    EVO is not a performance oriented drive. 850PRO is. And this was already discussed in other reviews/seperate articles.
    Reply

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