My 1TB mSATA Samsung 840 EVO SSD read speed slowdown, no regrets, there's a fix

Posted by Paul Braren on Oct 15 2014 (updated on Oct 1 2015) in
  • Storage
  • My-mSATA-Samsung-840-EVO-resting-on-2.5-inch-SATA-drive-adapter

    Back on Sept 5th, I excitedly opened up my new 1TB drive, from it's tiny box. I stared at it for a bit, in awe that 1TB could fit in such a small chip. I had eagerly anticipated getting this drive for some time, knowing I'd finally have some elbow room. I had been beyond 90% full on my 256GB SSD for some months. I also knew I was about to need much more storage, for an upcoming project. So I installed the drive, cloned it using Samsung's software, then tried it out first in the SATA2 speed mSATA slot on my ThinkPad W520 laptop I call tZilla. Worked quite nicely. I then tried it in an mSATA to SATA adapter, seated in the 2.5" traditional laptop drive bay that runs at SATA3 speeds (see also TinkerTry's Superguide: Timeline of USB, SATA, and Thunderbolt speeds). Once I turned on RAPID Mode, it performed a little better in the mSATA slot actually, which I found interesting. Anyhow, all indications were that my speeds were normal in either laptop slot, with a quick run of ATTO Diskbench confirming roughly 550MB/s read and write speeds. Awesome, ready for my heavy use during a lot of virtualization work I had planned, including resizing my encrypted C: drive (see details at Here’s a bunch of storage related stuff I learned this month, including experience with my new 1TB SSD). While I happened to be away from home here in Germany for a month, I noticed that resuming my large 5GB of RAM VM from suspend was slowing down. Something I was doing several times a day, actually. This was long after the debug mode speedup trick I outlined long ago here. So it was beginning to be a bit worrisome. I finally put two and two together during one of my recent weekend drives over The Netherlands, to meet up with some TinkerTry site fans. I happened to be listening to this PC Perspective Podcast #319, where the story of a slow-down with some SSDs was told. Driving on the Autobahn at the time, I used the steering wheel controls to jump back for a re-listen, and quickly realized that wow, Allyn was talking about my drive! When back online, I dug into this a bit, and quickly found these articles, detailing the tests for the problem, and the fix:

    Samsung 840 EVO Performance Fix Available Tomorrow by Sam Chen on Oct 14 2014, Custom PC Review.

    Samsung 840 EVO Performance Restoration Tool preview - Getting EVOs back up to speed by Allyn Malventano on Oct 14 2014, PC Perspective.


    Finally tonight, I was able to dive in and give the HD Tach 3.0.4 test a whirl (in XP Compatibility mode, when run from Windows 8.1). The findings (above) were obvious, looking very much like Sam Chen's "before" test pictured at left above. Yes, I have the problem. I'm actually glad, since I know why my large consecutive read performance was beginning to suffer a bit, such as resuming a suspended VM. Naturally, with warnings like Allyn's here:

    Samsung states you can use the drive during this process, but I would not recommend it, as you are tempting fate. Even if it is your OS drive, just leave the system idle for an evening if at all possible. Going further, I would highly recommend backing up the system prior to performing this update, as anything can go wrong. Out of five drives we tested the process on, one of them corrupted its MFT during the post-reboot process, and a subsequent reboot resulted in the loss of nearly all data. While MFT corrupted in a manner where the data could be recovered with forensic software (i.e. it was not TRIMmed), you don’t want to bank on that type of a recovery if something goes sideways during the update.

    I won't be dreaming of attempting this, while ~4,000 miles away from my automated daily backups. This is just in case I need to use my Windows Server 2012 R2 Essentials server for a bare-metal restore, should the fix go "sideways." I'll be back at home on Saturday, October 18th, and will be attempting this fix soon after. Note, I did read that it is possible the fix will disable RAPID Mode, at least temporarily. Do I regret my purchase of this beloved drive, that has thousands of 5 star reviews on Amazon? Nope, this is not a big deal to me, and wouldn't convince me to try other brands again because of this one bump in the road. I'm just too happy with having this much SSD space to be angry about such matters, which aren't exactly unusual. Heck, I've even been through the early days of the Intel X25-M, including a complete failure in 2 weeks that required a warranty replacement, followed by a slowdown that was severe, requiring me to re-image every 3-6 months. Yes, this early-days expensive SSD predated the TRIM command, and boy did it show. Another perspective on the 840 EVO read slowdown s that it seems likely to me that the rest of this drive's life will be uneventful, since Samsung is obviously watching this situation very closely, as there fix is rolled out to folks with this popular drive. Should you also choose to also go with an Samsung 840 EVO series of value SSDs, here's the affiliate link:


    available in a variety of sizes and form factors. Consider buying this tiny mSATA variant, and the mSATA to 2.5" drive SATA3 adapter, to give yourself the versatility of being able to choose which interface to use for a variety of situations:


    mSATA 1TB 840 EVO on adapter – Samsung Magician Performance Benchmark History [RAPID Mode On]

    Oct 20 2014 Update

    Good news. Did a full system backup yesterday, then kicked off the performance restoration utility, and slept on it, still shrugging off jet lag. Started my day today happy to see that my normal read speed performance was regained, as seen below. The speedup was also evident to me, when resuming my 6GB of RAM VM, this is good, results below:


    Confidence strengthened, I then went and did the same fix for another Samsung EVO in my family (256GB), and its speed is restored now as well. It would appear this incident may be behind me now, time will tell. But I'm not particularly worried about it, since this was never a serious issue, and fixing it wasted only a few minutes of my time.

    See also this outstanding PC Perspective video:

    Jun 08 2015 Update

    It's all about compensating for cell voltage drift over time,, which TLC SSDs are more sensitive to.

    I started to notice my Samsung 840 EVO 1TB mSATA drive slowing down again. The issue is most noticeable when resuming a 5GB of RAM VM from suspend, which I do daily. It's become about half as fast as it used to be.

    Samsung Magician 4.6 works for most other Samsung variants, but alas, not for the mSATA version, so the wait continues. Meanwhile, Samsung support actually advised me to consider using the free version of DiskFresh. Will give it a shot, as soon as I get a more recent Veeam Endpoint Backup FREE backup completed.

    What if my mSATA SSD was a in a VMware VMFS datastore role? Then such a Windows utility workaround like DiskFresh won't help me at all. What we home virtualization enthusiasts really need is a bootable ISO image to fix the drive firmware no matter what OS or filesystem is on there currently or in the future.

    Oct 02 2015 Update

    See also