Death and the unplugged SSD: How much you really need to worry about SSD reliability

The word is out: Your SSD won't retain your data forever when you unplug it. Yup, you'll never be able to go on vacation again without toting your SSD along. It's incapable of surviving for two weeks without you, poor thing.

I kid, of course.

Not archival, but not pathetic

The truth is, yes, under disastrously unfortunate environmental conditions (we're talking Biblical), your SSD could lose data retention just a few days after it's pulled from your PC. It could also lose it immediately if you pulverized it with a sledgehammer or threw it in a vat of sulphuric acid--almost-as-likely scenarios. To the point: I've re-tasked SSDs after a couple of years of sitting on the shelf, and annoyingly--I still had to secure-erase them to get rid of the old data.

This is not to belittle the underlying message that non-volatile memory media isn't forever, and in no way suitable for archiving. But panicking when you unplug the thing is unwarranted. SSDs are designed for speed and day-to-day use, but the amount of time they retain data when put on the shelf is measured in years, not days.

The current wave of concern is based on a table in a JEDEC presentation about general SSD specifications by Seagate's Alvin Cox. The table shows the expected data retention characteristics of SSDs at both operating and non-operational temperatures, using data culled from Intel research. It highlights a non-operational, ambient temperature of 87 degrees Fahrenheit as the cause of failure in data retention in client-side (consumer) SSDs after only a year. Notice that's not a few days. If you store your SSD someplace that averages 72 degrees Fahrenheit, a far more likely scenario, you're talking two-years-plus according to this table. Notice again, that's not a few days.

What the table warns is that data retention drops precipitously as ambient and/or operational temperatures rise above the norm. For instance, you could lose data after only a few weeks if your SSD is stored in Death Valley, during the summer, with no AC. The table ends at one week's retention at 131 degrees. Put your SSD in an oven at 450, and you're on your own.

Several of the SSD vendors I talked to said they'd expect their consumer products to do better, as in several multiples better, than this chart would indicate. But even 10 years is hardly an archival timespan, and SSDs simply shouldn't be relied upon for long-term storage.

Digital doesn't mean forever

NAND can't retain data forever, or even as long as other types of media (hard drives, optical) because it stores data as tiny, trapped electrical charges. The cages that contain these charges aren't perfect--they leak, or de-trap in industry lingo. True, they leak extremely slowly, but they leak nonetheless.

Also, as shown in the JEDEC specifications, the warmer they get, the faster they leak, and the faster operations wear them out. Cell degradation occurs whether an SSD is in use (powered/operational) or stored (unpowered/non-operational). That's a simplified explanation. If you really want to dig into it, there's plenty of info online.

NAND and SSDs have never been touted as archival storage, but those degradation facts are rarely highlighted. That's why we have this discussion every couple of years. That and the persistent consumer misconception, aided by misleading advertising and the lack of visible deterioration, that digital somehow means forever. 

In fact, no storage media is warrantied against data loss, only replacement. Seagate's hard drive warranty warns "This limited warranty does not cover data loss--back up the contents of your drive to a separate storage medium on a regular basis. Also, consequential damages; incidental damages; and costs related to data recovery, removal, and installation are not recoverable under this warranty."

Kingston's SSD warranty reads "Kingston is not liable for, and does not cover under warranty, any damages or losses of any kind whatsoever resulting from loss of, damage to, or corruption of, content or data or any costs associated with determining the source of system problems or removing, servicing or installing Kingston products."

You can go down the list of vendors. Get the picture

Don't worry--after you back up

It's a good thing this story reopened the discussion that SSDs, and NAND in general, are not suitable for archiving data. But you absolutely do not have to rush back from vacation or hire someone to turn on your PC every few days to avoid losing the data on your SSD. 

To archive data, store it online, store it to hard drives (write the data, unplug them, and store them in a safe place), or even use M-DISC write-once archival optical media. Yeah, and you thought optical was dead. Also, always follow the rule of three and keep a working copy of your data, a backup copy, and a copy of the backup.

Then, for goodness sake, relax and enjoy the amazing speed of your SSD!


Jon L. Jacobi

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