Samsung's 840 EVO SSDs were among the cream of the solid-state crop in 2013, boasting fast speeds and big-time storage capabilities at a (then) record low cost. But some buyers noticed a troubling occurrence: As time went on the drive's read performance could plummet, all the way down to sub-100MB per second speeds. That's a mammoth dip from the drive's claimed 520MBps maximum.
Fortunately, Samsung was able to identify the root cause of the problem--a combination of usual NAND cell degradation and an unusual NAND management issue--and issued a fix in Ocotber. Problem solved!
Not so fast. Some (but not all) previously affected users have reported seeing performance dip yet again after using Samsung's original patch. PC Perspective's Allyn Malventano rounded up numerous 840 EVO SSDs and found several drives with the issue, one of which he sent to Samsung for evaluation. Now, Samsung's released a statement to PC Perspective and AnandTech acknowledging that slowdown is still a problem for a small subset of 840 EVO users:
"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."
In other words, the initial fix isn't as much as a fix as it was originally thought. Samsung's still researching a more permanent solution, but releasing an update to (presumably, hopefully) refresh the "stale" data on affected SSDs in the meantime. It's better than nothing, I guess, but here's hoping Samsung solves this puzzle sooner rather than later.
One upside: These performance issues have been isolated to the Samsung 840 EVO alone. The newer Samsung 850 Pro and 850 EVO SSDs, which use bleeding-edge vertical NAND technology, aren't affected. No matter what type of solid-state drive you use, PCWorld's ultimate guide to SSD management can help you keep it running faster, longer.