I've been going through some disks that I had in USB 3.0 enclosures (they were all plain HDDs), and I found that:
- All of them didn't work. It seems that their power consuption is higher than some laptops can provide.
- After connecting them on a powered enclosure, they work but all of them ran hot (maybe lack of lubrication?).
- One of them developed read errors.

So, after salvaging everything I could, I put some SSDs in those enclosures. Reviewing the specs of the disks I found a line that said something like "Data retention (without power): 1 year". OK, I got it. If the disk is not used in a year, nobody guarantees that my data will be there. But how does it work?

I mean, on DRAM memories (the only analogy that I can think of) you need to "refresh" the RAM preiodically to avoid data corruption. How do you avoid data loss on SSD disks?
- It is enough to power them periodically to get the data refreshed?
- Maybe should I read the entire disk (i.e.: dd if=/dev/sdc of=/dev/null or running a SMART long test)?
- Or do I have to rewrite the entire contents?
- Does anybody had lost data because of letting it unpowered for a long time?
- Do "hybrid" (HDDs with SSD parts) disks suffer from same issues?