Over the last month there has been some concern over the read performance of Samsung’s 840 EVO drives, and whether after Samsung’s previous performance fix, that these same drivers are starting to regress in performance once again. Since then we have been pressuring Samsung for additional information on the issue and a response, and this afternoon Samsung has finally issued a statement on the matter.

In October, Samsung released a tool to address a slowdown in 840 EVO Sequential Read speeds reported by a small number of users after not using their drive for an extended period of time. This tool effectively and immediately returned the drive’s performance to normal levels. We understand that some users are experiencing the slowdown again. While we continue to look into the issue, Samsung will release an updated version of the Samsung SSD Magician software in March that will include a performance restoration tool.

As a reminder, the original 840 EVO performance degradation issue was a result of a combination of NAND cell charge decay and NAND management algorithm issues. While NAND cell charge decay is a normal part of NAND operation, it was something Samsung’s more complex TLC NAND was more sensitive to. Meanwhile Samsung’s algorithms, when faced with this decay, erroneously went into an aggressive read-retry state, which is ultimately what lead to the drop in read performance. Samsung’s fix in turn addressed their NAND management algorithm, and at least at the time was thought to be a permanent fix for the issue.

These more recent performance issues and now Samsung’s statement make it clear that the issue is unfortunately not as fixed as Samsung initially thought it would be. At this point Samsung isn’t saying what the root cause of this latest issue is, but it’s likely that this is a continuation of the original issue. In any case the upshot is that Samsung believes the issue can be corrected, however given the last fix it’s not clear whether this next fix will be any more a permanent fix than the last one.

Source: Samsung (via email)

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  • donawalt - Saturday, February 21, 2015 - link

    I went ahead and ran the performance restoration again and it made a huge difference.
    Before: degradation obvious at different spots:
    https://dl.dropboxusercontent.com/u/56053396/test1...
    After: performance consistently pegged at 512 MBps:
    https://dl.dropboxusercontent.com/u/56053396/test2...
    Reply
  • Achaios - Saturday, February 21, 2015 - link

    I ran HD TACH again, this time with no other software running in the background, and this time I got worse results:

    http://i.imgur.com/onAreoB.jpg

    It does seem like the perf of my 840 Evo has degraded slightly since January 7 2014 when I applied the last Samsung fix.
    Reply
  • aggiechase37 - Sunday, February 22, 2015 - link

    At this point, as far as I am concerned, if they don't replace these drives with something that doesn't doesn't break all the time, I will never buy another Samsung product again. Their phones have the worst reception in the business, their TV's are poor quality control (I had severe flashlighting issues on mine), their ssd's are clearly suspect, and being a heartbeat away from the one of the nuttiest countries in the world is not exactly reassuring. Samsung, replace these drives or you're dead to me. Reply
  • Achaios - Sunday, February 22, 2015 - link

    I am thinking the same too. Following this cluster you know what, I will never buy a Samsung SSD again and I will recommend the same to others. Updating my Overclock.net rig profile to include a note to that effect. Reply
  • EasterEEL - Sunday, February 22, 2015 - link

    I am using Samsung 830's myself but I have persuaded a couple of friends to by the 840 evo as they were very price sensitive. Check one at Christmas and it performance was definitely degraded so ran the tool to fix. Really disappointing to here the problem will come back. A company as big as Samsung should do the right thing as fobbing customers off with inadequate firmware fixes does nothing for credibility and customer loyalty. Samsung need to take a look at what Apple was eventually forced to do with the MacBook dry solder issue following a class action. Reply
  • Achaios - Sunday, February 22, 2015 - link

    I doubt that Samsung care. Unfortunately, by buying off cheap Samsung crap, we got "what we paid for" as the old saying goes, and that is cheap, inferior crap. Reply
  • Yongsta - Monday, February 23, 2015 - link

    No more Samsung TLC drives for me, I'm just gonna stick with Samsung PRO drives from now on, I never have any issue with those. Reply
  • Notmyusualid - Sunday, February 22, 2015 - link

    Indeed, price would usually play a part in it for me too - but as I was in South East Asia at the time of my purchases - I simply couldn't get my hands on the MLC Pro versions, so as only 840 TLC Evos were available, two of them it was for me.

    Meanwhile, my X25-E 64GB *still* chugs along without so much as a hiccup... I'm confident that I'll not fit anything less than an enterprise-class drive in a machine of MY OWN, again.

    But, not to pour scorn over Samsung alone here, I've seen a number of SSDs fail (one Intel MLC was DOA too), and I now do not keep any sensitive data on SSDs, it has all been moved to mechanical storage once again, and that is NOT due to the decreased cost / bit.

    Peace out...
    Reply
  • npz - Sunday, February 22, 2015 - link

    One thing that pisses me off about Samsung's firmware update system, both through Magician Windows software or DOS: it ONLY works on later generation Intel machines!! It's a long standing issue they acknowledge in their documentation but refuse to fix.

    That means if you're using the 840 EVO on an AMD system or older Intel (775 socket) you're screwed!
    Reply
  • Gigaplex - Monday, February 23, 2015 - link

    Worked fine on the AMD systems I tried it on, using the standard msahci driver. Reply

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