Back in the days when mechanical hard drives with spinning platters were the norm, you could simply hand your old hard drive to a deserving relative or friend as an upgrade, get a thank you, and call it a day. It's not so simple with today's solid-state drives.
In many cases, used SSDs simply aren't as fast as newer ones. The biggest issue in retasking, reselling, or even maintaining an SSD for a prolonged period stems from an inconvenient characteristic of NAND flash memory: Previously written cells must be erased before they can be rewritten with new data. If the SSD is forced to reuse cells rather than use new ones while storing data, performance will plummet.
To avoid this problem with NAND flash memory, modern SSD controllers use a number of tricks, including building in extra capacity that users can't touch--a technique known as over-provisioning. There's also a command called TRIM that tells an SSD when blocks of memory are no longer needed and can be consolidated and erased.
Sounds good, right? But there's a catch.
Better in theory than in practice
Not all garbage collection (as the cleaning up of an SSD's NAND is known) is created equal. It doesn't run constantly, and some older operating systems don't even support the TRIM command. As such, more "used" NAND cells are left hanging around on your SSD than you'd suspect, according to nearly every vendor and data-recovery specialist I consulted
After prolonged use, these idle cells can add up to a big hit on your SSD's performance. That's not good.
Simply deleting files and repartitioning and formatting your drive won't do the trick, however, as those operations take place at levels above where true garbage collection occurs. In fact, due to the total absence of utilities that force complete garbage collection, there's only one way to return an SSD to pristine, like-new condition--the ATA secure-erase command.
Secure erase to the rescue
Secure erase, a function built into every ATA-based drive since 2001, erases everything on a drive and marks the cells as empty, restoring the drive to factory-fresh default performance.
Once upon a time, you could invoke secure erase only via command-line utilities such as Linux's HDparam or the DOS-based HDDerase, developed by the University of California San Diego (with funding from the NSA, incidentally). But now, many SSD and hard-drive vendors provide a free utility--such as OCZ's ToolBox, Samsung's Magician, or Seagate's SeaTools--that provides a secure erase capability.
Note that while the command is standard, many vendor utilities work only with their company's products. If your vendor doesn't provide a secure-erase command, you can use the DriveErase utility found in the stellar Parted Magic software.
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