[UPDATE] Two Samsung 840 Pro review samples received by Anandtech have failed. [Edit] The non pro 840 Anand had has also now failed along with 4x 840's at [H]ardOCP http://hardforum.com/showpost.php?p=1039330548&postcount=65 Looks like the drive reliability list should look a little like this. Samsung 830 ( 27nm Toggle-mode MLC NAND ) "rock solid reliable" Samsung 840 Pro ( 21nm 2bpc MLC NAND ) Not so good - 6 have failed... Samsung 840 ( 21nm 3-bit-per-cell MLC (aka TLC NAND) - also may not be reliable - 1 has failed. As they continue to shrink Nand, it looks like they are reducing lifespan, reducing reliability all for the sack of reducing cost. I guess the older mature 25nm/27nm NAND SSD's are the way to go. Linkage - http://www.anandtech.com/show/6328/samsung-ssd-840-pro-256gb-review/8 "Update: Our replacement 840 Pro also died prematurely, I'd recommend holding off any purchases until we hear back from Samsung as to the cause of death."