In fact SSDs are not designed to retain data over very long periods while powered down.... particilarly when exposed to higher temperatures, and if they have seen lots of writes.
The interesting note from this abstract is I guess they saw that number of writes didn't seem to play as much of an effect. I don't known if they tested temperature as an independent variable.
I suspect higher temps played a role in influencing Google's results. Higher temps while powered on will increase write endurance. If they were ever powering off drives for efficiency purposes this would also have an effect on read errors, which also gets worse with higher temperature.
I'll quote heavily from AnandTech's article on the topic;
"As always, there is a technical explanation to the data retention scaling. The conductivity of a semiconductor scales with temperature, which is bad news for NAND because when it's unpowered the electrons are not supposed to move as that would change the charge of the cell. In other words, as the temperature increases, the electrons escape the floating gate faster that ultimately changes the voltage state of the cell and renders data unreadable (i.e. the drive no longer retains data).
For active use the temperature has the opposite effect. Because higher temperature makes the silicon more conductive, the flow of current is higher during program/erase operation and causes less stress on the tunnel oxide, improving the endurance of the cell because endurance is practically limited by tunnel oxide's ability to hold the electrons inside the floating gate."
The interesting note from this abstract is I guess they saw that number of writes didn't seem to play as much of an effect. I don't known if they tested temperature as an independent variable.
I suspect higher temps played a role in influencing Google's results. Higher temps while powered on will increase write endurance. If they were ever powering off drives for efficiency purposes this would also have an effect on read errors, which also gets worse with higher temperature.
I'll quote heavily from AnandTech's article on the topic;
"As always, there is a technical explanation to the data retention scaling. The conductivity of a semiconductor scales with temperature, which is bad news for NAND because when it's unpowered the electrons are not supposed to move as that would change the charge of the cell. In other words, as the temperature increases, the electrons escape the floating gate faster that ultimately changes the voltage state of the cell and renders data unreadable (i.e. the drive no longer retains data).
For active use the temperature has the opposite effect. Because higher temperature makes the silicon more conductive, the flow of current is higher during program/erase operation and causes less stress on the tunnel oxide, improving the endurance of the cell because endurance is practically limited by tunnel oxide's ability to hold the electrons inside the floating gate."
See: http://www.anandtech.com/show/9248/the-truth-about-ssd-data-...