SoylentNews is people
SoylentNews
How do you destroy an SSD?
First, let's focus on some "dont's." These are tried and true methods used to make sure that your data is unrecoverable from spinning hard disk drives. But these don't carry over to the SSD world.
Degaussing – applying a very strong magnet – has been an accepted method for erasing data off of magnetic media like spinning hard drives for decades. But it doesn't work on SSDs. SSDs don't store data magnetically, so applying a strong magnetic field won't do anything.
Spinning hard drives are also susceptible to physical damage, so some folks take a hammer and nail or even a drill to the hard drive and pound holes through the top. That's an almost surefire way to make sure your data won't be read by anyone else. But inside an SSD chassis that looks like a 2.5-inch hard disk drive is actually just a series of memory chips. Drilling holes into the case may not do much, or may only damage a few of the chips. So that's off the table too.
Erasing free space or reformatting a drive by rewriting it zeroes is an effective way to clear data off on a hard drive, but not so much on an SSD. In fact, in a recent update to its Mac Disk Utility, Apple removed the secure erase feature altogether because they say it isn't necessary. So what's the best way to make sure your data is unrecoverable?
(Score: 4, Informative) by Immerman on Friday March 17 2017, @08:39AM
As others said, SSDs work fundamentally differently than HDDs. Most importantly in the fact that HDDs use physical addressing - when you say "access sector 17" it goes out to sector 17 and accesses it. A SSD though uses logical addressing and instead goes to a lookup table to find out "okay, logical sector 17 is currently mapped to physical cell 94", and then goes to access cell 94 - all completely invisible to the PC.
So you write sensitive data to "sector 17", which actually ends up in cell 94. Then you try to overwrite it - "write this garbage to sector 17" - and the SSDs wear leveling algorithm goes out and grabs whatever least-used cell is available, maybe 106, and writes your garbage to that, and updates the logical sector map to say 17 now maps to 106. Cell 94, which still contains your sensitive data, never gets touched.
So you figure, heck, I'll just overwrite *everything*, that'll catch it, right? Wrong, because SSD manufacturers know that neither their manufacturing nor wear leveling are perfect, and some cells will wear out long before others. So they include a bunch more cells than are addressable by the PC so that it has "spares" to replace cells that wear out. PC thinks SSD has 100 sectors, but it actually has 120 cells. fill the drive with garbage, and all the current "extra" cells remain untouched. If you're lucky a few consecutive re-writes will bring cell 94 back into circulation and it will get overwritten, but there's no guarantee of that. And if you're unlucky, the first time it goes to update cell 94 it notices that it's about to wear out, and so dumps it in the "broken" pile, data and all, never to be touched again. Unless someone desolders the containing chip and puts it in a chip reader, in which case there's your data.
There's really only one way to reliably wipe the data - store it as random garbage in the first place (aka encrypted), which many/most SSDs support natively, so that when you destroy the keys there's no longer any way to turn the garbage back into data.
Many drives offer a "disk wipe" option as well, a special command that rapidly internally deletes *everything*, but due to the nature of SSD cell failure, you can't count on that if it's important - failing cells tend to become write-resistant while still being readable, so just because the drive *thinks* it wiped a cell, doesn't mean he previous data is actually gone.