http://www.myce.com/news/samsungs-tlc-n ... ear-72798/
http://www.anandtech.com/show/8550/sams ... on-the-way
Samsung has acknowledged their 840 Evo SSDs have a problem whereby files which have not been modified or written to for an extended time read far slower than usual, and are working on an updated firmware to fix the problem. There have been no reports of any read errors or data lost as a result, however.
As a result of this, I have changed the recommendation for the performance PC configurations to an Intel 530 SSD.
