Samsung has announced imminent arrival of the 850 Evo SSD -- the first mainstream SSD that uses 3D NAND. Thanks to its fancy 3D NAND tech, the 850 Evo is one of the fastest SSDs on the market -- and the longevity and reliability of 3D NAND TLC flash cells is so much better than standard planar NAND flash that Samsung offers the 850 Evo with a five-year warranty. There is one problem with the 850 Evo, however: It isn't priced quite right for a mainstream drive.