Earlier last year Samsung's 840 EVO SSD had certain issues with the sequential read performance which was quickly fixed by Samsung and in recent months those issues showed up once again. Samsung has announced that it is currently investigating these new performance issues and is preparing a new fix.
Back in October, Samsung has released a tool that fixed slowdown issues with 840 EVO sequential read performance which was reported by a small number of users after the drive was not used for an extended period of time. In last few months there have been new reports of a performance degradation and Samsung has announced that it is currently investigating these issues and will release an updated version of the Samsung SSD Magician software in March that will include a performance restoration tool.
In case you missed it before, the earlier performance degradation issues on the 840 EVO was a result of a combination of NAND cell charge decay and NAND management algorithm issues which Samsung managed to quickly fix. Although it was originally believed that this would be a permanent fix, it appears that this is not a case as Samsung will need to make a new fix for it.
In any case, you might want to check out the sequential read performance in case you own a Samsung 840 EVO SSD and wait for the new SSD Magician software which should launch in March.
Source:
Anandtech.com.