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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  • hojnikb - Monday, December 8, 2014 - link

    Or 50$ less and get a mx100/ultra II Reply
  • apoe - Tuesday, December 9, 2014 - link

    $10 more than the 250GB 850 Evo and you can get a 480GB Crucial M500 or TWO Sandisk Ultra II's. Even though it's a year and a half old at this point, for most end users the speed difference is negligible but the doubled capacity is not. Like the article says, the pricing (at least the MSRP) seems to be in a weird place... Reply
  • HisDivineOrder - Wednesday, December 10, 2014 - link

    Samsung thinks they're Apple.

    In SSD's.
    Reply
  • alacard - Monday, December 8, 2014 - link

    thanks for the review. is it my imagination or is the 120gb model missing from the destroyer benchmark? Reply
  • Kristian Vättö - Tuesday, December 9, 2014 - link

    I don't usually run the 2013 suite on 120/128GB drives because it's more geared towards large and higher performance drives. Users with such heavy workloads shouldn't be buying small drives anyway for performance and capacity reasons. Reply
  • Memristor - Monday, December 8, 2014 - link

    Regarding the price, newegg.com already offers them below the suggested retail price. See here:
    http://promotions.newegg.com/samsung/14-6480/index...
    Reply
  • wallysb01 - Monday, December 8, 2014 - link

    Only by $10. That’s not really enough. I got the 480 GB Ultra II for $160 over black Friday, that’s $90 less than this sale on the 500GB 850 EVO. That was maybe an atypically good deal, but even at more regular discounts the Ultra II/MX100 is priced at about $180-$190, maybe $200, which is more like $50-$70 less than this “sale” price 850 EVO.

    This review is right. Until the price comes down ~$50 per 500GB, I don’t see much reason for people buy the 850 EVO.
    Reply
  • fokka - Monday, December 8, 2014 - link

    comparing msrp to a black friday deal doesn't make sense. Reply
  • Luscious - Monday, December 8, 2014 - link

    Where's the m.2 version?

    And if Samsung is stubbornly sticking with 2.5 inch drives, why no Sata Express version?

    The hardware for both is out there, and has been for some time.
    Reply
  • ZeDestructor - Monday, December 8, 2014 - link

    It's a SATA drive, so the interface will be SATA and not SATA Express/PCIe. Consequently, an M.2 variant will perform the same, since those variants would also be SATA driven, much like the older mSATA drives - same thing, different form factor, and unnecessary to review seperately. Reply

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