Sadly enough, the old data read issue has been present on the Samsung 840 EVO series solid state drives since their initial release in 2013. The bug appears in the form of constant old data read performance degradation over time, meaning, the older the files on the 840 EVO drive get, the slower the drive will read them. However, if the old drive content is freshly rewritten, the read performance will be at its peak for some time before it starts to decay again. Samsung was well aware of this issue and its attempt at fixing it was the release of the EXT0CB6Q firmware, however, most users are reporting the aforementioned problem is still ailing the 840 EVO series solid state drives.
I have been running two Samsung 840 EVO 120GB drives in RAID0 configuration for a few moths now, long enough to be able to share my read performance results with you.
Test setup: ASUS P6T Deluxe / Intel Xeon X5670 / 12GB 1600MHz RAM / 2x120GB Samsung EVOs. Please note I am running quite an old motherboard lacking the SATA3 support, which means I am limited to only SATA2 speed. Ideally, I should expect the read speed of up to ~600MB/s (300MB/s x 2 because of RAID0).
Before I begin testing the performance of my RAID0 array, here is the screenshot ensuring both drives are healthy as well as on the latest firmware, the EXT0CB6Q (pic. 2).
Back in December of 2014, I ran the DiskFresh utility to fully restore the drives read performance and I have been monitoring it since. The array has 160GB of free storage space. Let’s take a look at the read performance in HD Tune, shall we?
As seen in picture 3, the integrated SATA2 controller is capable of sustaining the read speed of 540MB/s on average in RAID0. Maximum and minimum speeds are pretty close to the reported average, which is good news. One month later (31st , Jan.) things start to look a bit worse. Although the average and maximum speeds did not change much, the minimum read speed is another story here as it went down from the respectable 494MB/s to 382MB/s in just a moth’s time. If you pay heed to the speed graph, the second run looks much less consistent compared to the first one. The last, third run is the reason I decided to compile this post on my blog. You can see the average and minimum read speeds went down even further and hit the record low of 410 and 115 MB/s respectively. Not to mention, the graph has become extremely inconsistent and shameful to look at in just two months’ time.
Speaking from a real-world performance standpoint, all I have noticed is Windows 7 now takes about 14 seconds to boot in comparison to 10-11 seconds it would take in December, 2014. Although ~3 seconds does not seem like a long period of time, it actually accounts for a whopping ~30% of increase! That being said, I am still reluctant to run the DiskFresh utility every two months or so, as frequent SSD content rewrites do take a bad toll on the TLC-based drive’s longevity.
The good thing is Samsung has reported to be working on a new firmware update addressing the issue, which, hopefully, turns out fine this time.
Update 2nd April, 2015
It has been another month without a firmware update addressing the old data read speed degradation issue and it looks like the speed has gone down big time. Twice to be exact.