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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  • eanazag - Monday, December 8, 2014 - link

    Turbowrite is a default feature. It is marketing speak for optimizations to increase write performance in write workloads. It can't be turned on or off. Reply
  • erple2 - Wednesday, December 10, 2014 - link

    Well, it has to be able to be turned on/off, as Kristian has a chart showing the difference in write speeds with it on/off. However, unlike "RAPID", there is no downside to leaving it on. Reply
  • geniekid - Monday, December 8, 2014 - link

    Well written conclusion. Reply
  • andrewbaggins - Monday, December 8, 2014 - link

    It's hard to understand why your SSD reviews fail to include Idle Power Consumption charts. For the hundreds of millions of PCs and laptops in use which do not support the so-called Slumber Power it would be far more useful if you included a chart for typical or average power consumed during Idle state. Reply
  • metayoshi - Monday, December 8, 2014 - link

    "Hundreds of millions of PCs and laptops in use which do not support the so-called Slumber Power."

    Woah... I don't know where you got that "hundreds of millions" number from, but any system that supports SATA is able to support Slumber. Slumber has been in the SATA spec since forever, and pretty much all 2.5" drives, and some 3.5" drives support this power state.
    Reply
  • metayoshi - Monday, December 8, 2014 - link

    P.S. As an example, I have a Core 2 Quad Q6600 sitting in my cubicle at work on an Asus PSE WS Pro motherboard. I have no Idea how old this thing is, but it's running a SATA-II 3.0 Gbps interface, and that great grandfather of a system supports HIPM+DIPM, and does Partial and Slumber on a variety of SSDs and HDDs. Reply
  • eanazag - Monday, December 8, 2014 - link

    Newegg has a promotion for these drives ending 12/14/14 (US $) -
    120GB @ $89.99
    250GB @ $139.99
    500GB @ $249.99
    1TB @ $469.99
    Reply
  • eddieobscurant - Monday, December 8, 2014 - link

    I think an 120gb 850 evo usb thumb drive would be awesome . Reply
  • dwade123 - Monday, December 8, 2014 - link

    Realworld: all modern ssds have similar windows boot and game loading time. All these synthetic tests are just for reviewers to have something talk about, and marketing purposes. Meh. Reply
  • StrangerGuy - Monday, December 8, 2014 - link

    I would rather want a SSD that has 90% of a MX100 but only 50% dollar per GB, instead of extra performance that 99% of SSD buyers will not never benefit for more money. Reply

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