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No, Your SSD Won't Quickly Lose Data While Powered Down
An anonymous reader writes: A few weeks ago, we discussed reports that enterprise SSDs would lose data in a surprisingly short amount of time if left powered off. The reports were based on a presentation from Alvin Cox, a Seagate engineer, about enterprise storage practices. PCWorld spoke to him and another engineer for Seagate, and they say the whole thing was blown out of proportion. Alvin Cox said, "I wouldn't worry about (losing data). This all pertains to end of life. As a consumer, an SSD product or even a flash product is never going to get to the point where it's temperature-dependent on retaining the data." The intent of the original presentation was to set expectations for a worst case scenario — a data center writing huge amounts of data to old SSDs and then storing them long-term at unusual temperatures. It's not a very realistic situation for businesses with responsible IT departments, and almost impossible for personal drives.
We have a long-term (over several years) exercise where we collect large amounts of data at a very hot waterside location overseas, in an air-conditioned office. And then the racks get moved to a non air-conditioned warehouse where they sit for a year or longer. And then we come back after a year or longer, move the racks back into office space, and do the next iteration.
We were thinking about going to SSD, just for the drive performance, and we now know that our setup is a poster child for the problem that the alarmist article described.
Of course, we copy off the valuable data and take it home, but coming back to random corruption on our system and middleware drives could introduce some real issues.
How do you turn off your computers? And do your storage drivers put the drive into low power mode prior to turn off?
The thing with SSDs (and you don't appear to use the OEM ones like Samsung, Intel or Toshiba) is power failure can be deadly. Modern SSDs are fast and because SATA3 is a bottleneck, many sacrifice speed for data protection (if you can do 1GB/sec, and SATA3 is limited to 540MB/sec, you can sacrifice 40% of the speed in the name of data safety).
SSDs require a bunch of tables to work - the tables manage the flash translation layer software (the software that maps physical flash blocks to what the drive exposes, including wear levelling, TRIM and other features). In data safe SSDs, those flash tables are usually write-through cached so updates are committed to media, and so media always contains a consistent table. (There are tricks done to ensure that even if the table is partially written, there's a recovery table which is an older version. Think of it like a journaling file system).
Older SSDs cached the tables in RAM, wrote to them in RAM, then relied on a bank of capacitors to let them flush the tables from RAM to media on power loss.
Some SSDs cache them into RAM, and don't handle power failure, which can result in failures if the tables are corrupted.
The GOOD news is there's often a way to recover them - if you do an ATA_SECURE_ERASE command, it forces the SSD to reset the tables to a blank state and will often get them completely operational again, albeit losing all your data.
I put all my flash media (SSDs, SD-Cards, thumb drives) in a ziploc bag to protect them from condensation, put that inside a sealed mason jar (just in case there is a pinhole in the ziploc bag), and then put that in the bottom drawer of my refrigerator, right next to my battery stash.
This seems unwise. Packaging everything up in an airtight container under presumably room temperature and proceeding to put it in the fridge to "protect them from condensation" is great way to generate condensation.
You might want to consult a psychrometric chart or invest in desiccant.