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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  • ThisWasATriumph - Friday, February 20, 2015 - link

    Well I just checked mine for the first time since running the tool when it came out and it does look like performance has degraded on certain parts of the disk again...
  • Oxford Guy - Saturday, February 21, 2015 - link

    Funny how the tech site headlines last time read "Samsung releases firmware patch that fixes 840 EVO slowdown". They didn't say "claims to fix". Reply
  • MrSpadge - Saturday, February 21, 2015 - link

    Funny how you're complaining here at AT when their headline was just:
    "Samsung Releases Firmware Update to Fix the SSD 840 EVO Read Performance Bug"
    and write in the conclusion:
    "It's too early to say whether the update fixes long-term performance, but Samsung assured that the update does actually fix the NAND management algorithm and should thus be a permanent fix."
  • Flunk - Saturday, February 21, 2015 - link

    Lack of reading comprehension is the easiest way to spot trolls. Reply
  • xype - Sunday, February 22, 2015 - link

    Dude, Android has _nothing_ on the iPhone!

  • Oxford Guy - Sunday, February 22, 2015 - link

    Exactly, since Spadgie forgot to read and comprehend "last time". Reply
  • Oxford Guy - Sunday, February 22, 2015 - link

    No, what's funny (not really, actually) is your inability to read my post. Reply
  • alexrw - Sunday, February 22, 2015 - link

    Indeed. I just checked my 500GB 840 EVO and also took a hit: http://1.ii.gl/_1iFzMZWn.png Reply
  • biofishfreak - Friday, February 20, 2015 - link

    I've definitely noticed a drop in performance on my drive, and am glad they are still trying to resolve the issue.
    Please note, the above results are using Samsung's own Samsung Magician software. For reference, I applied the original performance fix software a week after it was released and currently have 4.64TB bytes written.
  • colinw - Friday, February 20, 2015 - link

    Kicking myself daily for purchasing this drive. Reply

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