I think there are two different issues that need to be addressed: endurance VS retention.
Endurance for all practical purposes is good, very good especially with 3D MLC NAND.
Not so good if you're dealing with a small, planar TLC drive using cheap NAND.
Cold data retention on the other hand is something to be concerned about.
Let me repost what I wrote on Anandtech:
Well I respond because one situation where you absolutely cannot use SSDs for is cold storage,
like offline archiving and cold redundancy (whole machines you keep offline as backup). Less so for online archiving.
"Data retention is the timespan over which a ROM remains accurately readable. It is how long the cell would maintain its programmed state when the chip is not under power bias. Data retention is very sensitive to number of P/E cycle put on the flash cell and also dependent on external environment. High temperature tends to reduce retention duration. Number of read cycles performed can also degrade this retention."
The more enterprise oriented the drive gets, the worse its data retention rates are. In fact not only do PE cycles degrade retention, but also READs!
NAND Technology = Data Retention @ rated P/E cycle
SLC = 6 Months
eMLC = 3 months
MLC = 3 Months
planar TLC is even worse.
While the above is Dells published retention rates for their SSDs at max rated PE cycle, realize that it's not a binary situation as it continuously degrades. So it could be a few years. Nonetheless, cold storage is out of the question. So is read-oriented archiving over the very long term.
Consumers got a taste of the data rentention issue inherent in SSDs with the Samsung 840 EVO. The fix was to periodically rewrite old pages. But that only works if you plug the drive in.
In addition, tempurature affects the retention rates. The hotter, the worse, and that's while on the shelf in storage!
JEDEC is supposed to guarantee a drive can retain data one year, but there have been reports that barely used drives have had issue when left unpowered.
This happened to some users for Crucial MX100 and MX200:
"had a MX100 that I tucked away for about 8 months (unpowered, just to test data retention)"
lost its security settings and required a PSID revert.
Now one can give them the benefit of the doubt and assume the security keys could be on a different part of the drive that is not part of the data NAND. Still that does not bode well.
While there's speculation that it's a firmware bug, I personally don't think it is actually a firmware bug because why would it happen after leaving it unpowered? Using Samsung's 840 fix of refreshing old pages would not help either since that requires having the drive powered. Perhaps there will be a fix by firmware but I am guessing it would be working around the problem. The whole thing is symptomatic of a analog hardware issue.
Retention me reminds of (gas) car batteries and the need to occasionally start them and leave them running for a while to recharge the batteries.Edited by npzeyer - 10/9/16 at 5:00am