Performance Consistency

Performance consistency tells us a lot about the architecture of these SSDs and how they handle internal defragmentation. The reason we don’t have consistent IO latency with SSD 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 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 buttons 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.

  WD Black2 120GB Samsung SSD 840 EVO mSATA 1TB Mushkin Atlas 240GB Intel SSD 525 Plextor M5M
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The area where low cost designs usually fall behind is performance consistency and the JMF667H in the Black2 is no exception. I was actually expecting far worse results, although the JMF667H is certainly one of the worst SATA 6Gbps controllers we've tested lately. The biggest issue is the inability to sustain performance because while the thickest line is at ~5,000 IOPS, the performance is constantly dropping below 1,000 IOPS and even to zero on occasion. Increasing the over-provisioning helps a bit, although no amount of over-provisioning can fix a design issue this deep.

  WD Black2 120GB Samsung SSD 840 EVO mSATA 1TB Mushkin Atlas 240GB Intel SSD 525 Plextor M5M
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  WD Black2 120GB Samsung SSD 840 EVO mSATA 1TB Mushkin Atlas 480GB Intel SSD 525 Plextor M5M
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TRIM Validation

To test TRIM, I first filled all user-accessible LBAs with sequential data and continued with torturing the drive with 4KB random writes (100% LBA, QD=32) for 30 minutes. After the torture I TRIM'ed the drive (quick format in Windows 7/8) and ran HD Tach to make sure TRIM is functional.

Based on our sequential Iometer write test, the write performance should be around 150MB/s after secure erase. It seems that TRIM doesn't work perfectly but performance would likely further recover after some idle time.

The Drive & The Test AnandTech Storage Bench 2013
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  • nitram_tpr - Thursday, January 30, 2014 - link

    Ouch, that is one expensive drive. As you say, it appears to be the ideal solution for a laptop with only a single drive bay. I think there is another option - change the HDD for an SSD and put the HDD into the optical drive bay with an adapter. Reply
  • ddriver - Thursday, January 30, 2014 - link

    It is kind of expensive and kind a slow and power hungry for an SSD, but still it is essentially 2 hard drives in one. I would actually get this if the SSD part was a tiny bit better. I don't think the presence of mechanical drive in the case mandates the SSD performance be any lower. I think I will just install an extra drive in the optical drive bay, seriously DELL what were you thinking who uses optical storage in 2012? Reply
  • lmcd - Thursday, January 30, 2014 - link

    Me.

    Thanks Dell for considering :-)
    Reply
  • ddriver - Thursday, January 30, 2014 - link

    Poor you :) I maintain about 20 TB of data, in the past the database was much smaller so I used to back it up on CDs, then DVDs, but the damn things are just too slow, unreliable, small and the cost of storage was very high. It was this moment I began hating optical storage with passion, my life got marginally better when I destroyed all optical disks and moved everything to hard drives - faster, cheaper, more compact and reliable.

    I know manufacturers provide installation disks which some people end up using for years, failing to realize the software on that disk is usually out of data before they even made the purchase.

    And for all scenarios a hard drive is overkill there is the USB flash drive.

    I guess optical storage makes some sense on consoles and/or media center PCs, if you watch many bluray or dvd movies, but for everything else... meh... and on that dell laptop it is just dead weight and battery drain.
    Reply
  • Morawka - Thursday, January 30, 2014 - link

    Try blu ray man, blu ray's will match HDD's capacity in the near future. At present, it can already match SSD's capacity of 128GB.

    The blu ray tech is good up to 25 layers @ 32 GB per layer = 800 GB

    Optical is far from dead when America has some of the worst bandwidth in the world.
    Reply
  • Gigaplex - Thursday, January 30, 2014 - link

    So I'd need 5 Blu-ray discs per hard drive, which would take 15 hours to write at 16x speed. Reply
  • JHBoricua - Thursday, January 30, 2014 - link

    But what happens when one of those 4TB drives fails? Assuming you have them in a RAID array, it will probably take as long or longer for the array to rebuild, not to mention that at those capacities, the risk of another drive failing during the rebuild are simply too great if you care about your data. Reply
  • ddriver - Friday, January 31, 2014 - link

    I don't raid, I just backup. This is IMO better. I could raid something for performance but never for safety. Reply
  • name99 - Friday, January 31, 2014 - link

    Jesus, You sound like iOmega with the endless succession of ZIP and JAZ drives, or Cringely talking up his aluminum foil based drive (which still has not seen the light of day).
    So the best Blu-Ray could do (in drives that don't exist, using disks that don't exist) is a very slow version of a drive that I can buy for around $50?
    Good luck getting rich with that particular technology.

    Optical is dead dead dead. And quit whining about "worst bandwidth in the world" you drama queen. Go to a real third world country and see what really bad connectivity looks like. The only problem most Americans have is that they will have to wait five minutes for their drivers to download rather than 20 seconds. That's just not enough pain to keep optical relevant.
    Reply
  • TheinsanegamerN - Saturday, February 1, 2014 - link

    you forget the very restrictive bandwidth caps, the terrible customer service, the awful reliability, the throttling of data, the list goes on. Reply

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