Thought I'd post a series of troubleshooting tips received from Crucial. Yesterday, my 512gb SSD completely quit responding, even to the point of not mounting on any drive or external case. I emailed Crucial/Micron, thinking the drive was defective. Apparently it likely isn't. I was using it as an OS drive, but upon replacing my 17" machine with a retina mac, I put the drive in an external USB3 case. ************************************************* Hello Kenneth Thanks for contacting us. The behavior you are describing is consistent with TRIM commands not executing on the drive (which may result from lots of writing and rewriting, especially OS installs, not done on the OS level). The accumulation of 'junk' data from file deletions, even reformats, basically clogs up the drive and reduces or sometimes even halts performance and can even dismount the drive. A secondary feature called Garbage Collection activates when the drive is powered, but has no data throughput, for an extended period, and does background cleanup on our SSDs which can make up for the lack of TRIM. If this is the cause of your drive's behavior, a period of idling the drive without any data being written or read actively will improve its performance. We recommend you perform this idle period on a desktop computer because it allows you to only connect the SATA power connection. However, a USB enclosure with an external power source will also work. A laptop computer will also work, but youll have connect the drive and navigate to the systems BIOS menu. (Please refer to your system manufacturers documentation on how to access the BIOS.) For laptops, we dont recommended using a USB enclosure powered via USB; dedicated AC power is preferable. In addition, Apple laptop users must hold the Option key while they power on the system (with the SSD installed). This will boot the Mac to the Startup Manager screen. The Startup Manager screen works like the BIOS screen on a laptop, in that it gives the drive power without any data throughput. An alternative Apple method is to close all open programs (including background processes) after startup and idle on your desktop. Just power the drive and let it sit, preferably overnight, but even a few hours should improve performance if this is the cause of your drive's erratic performance, though full Garbage Collection takes 8-24 hours and should be resumed when you can be without that system for an extended period. If you have further questions, please visit the Crucial Community at http://www.crucial.com/help. For sales questions, try our online chat service at http://www.crucial.com/company/contacts.aspx. Our hours are Monday through Friday from 7 a.m. to 6 p.m. (Mountain Time). At Crucial, we are committed to providing high-quality products and reliable service and support.