Probably the best single point I've heard. This is undeniably true, of course and impossible to argue. And of course, I was in fact asking, because I wanted to know whether this SSD potency talked about online was really at a point of being able to replace HDDs long term.
Yeah there's a lot of marketing talk. I don't think they're going to replace HDD's anytime soon for actual backup usage. SSD endurance tests have occurred, but almost no-one is doing "cold storage" data retention tests. As a "working" drive, SSD's are generally reliable because part of the background maintenance of an SSD will correct / rewrite any data which is getting hard to read. That's how the "fix" for the Samsung 840/EVO drives works. With MLC you've got 4x voltage states 0v, 33%, 66% and 100% of whatever voltage is used. With TLC, you've got 8 (0v, 14%, 29%, 44%, 58%, 72%, 86%, 100%). With the latter, the "gap" between each state is much less. The smaller the cells used (40nm, 25nm, 19nm, 16nm, etc), the fewer electrons hold that state, and the greater risk there is of one voltage "drifting" into another. This will be more likely to occur in an "offline" drive where no power = no checking & rewriting of "borderline" data. The only vague figures I've found was related to the Samsung 840 debacle. Basically,
40 weeks for 21nm TLC and as little as 8 weeks for 16nm TLC. MLC will last longer, as will larger cell sizes (eg, 40nm V-NAND), but again, no actual solid figures are available for MLC vs TLC drives in general or Samsung's new 40nm 3D process. Personally I don't like TLC drives at all. There are just too many unknowns.
1. So, I should cycle the content of the one currently in use every two years? So, A(in use) copy to B, B > C, C > A? Is that the idea?
The "rewrite every 2 years" was just a simple example of what you could do with multiple backup drives to make absolutely sure. If you've only got one backup drive, then there's a risk (if small) of losing everything every time you plug it in. I have hard disks with 5 year old data and a relative's laptop had 8 year old data with no readability problems. You don't need to rewrite data literally every 2 years, it's just that by cycling them, the content will never be older than 4 years on any drive (or 2 years if you did it annually) and you'll always have one drive that's totally unplugged when the other two are plugged in. Maybe that sounds paranoid, but I knew a guy who swore blind his 4x drive RAID1 NAS was super-safe (same data mirrored on 4 drives) - until an indirect lightning strike took it (and all 4 drives) out with a surge that blew straight through his surge protector... Since then I've always made sure at least one backup drive is totally offline whilst the others are connected. Aside from surge / electrical problems, it also safeguards against accidental deletions being "mirrored", viruses / "ransomware" / malware wiping stuff out, etc.
2. I'm assuming anti-static sleeves in a dry place isn't enough. Are there recognised storage cases/boxes etc for hdds to really sit for long times well? At least as safely as possible?
I haven't looked into this side of things, though I've had no problem keeping them in an anti-static bag inside a bubble wrap bag. As long as they're not subject to strong magnetic fields, vibration or temperature variations (don't keep them in an unheated garage/shed), there's little more you can do. From what I understand, modern "fluid bearing" HDD's don't tend to seize up unlike ye olde ball bearing spindle drives.
3. If storage is the primary use of these drives, is cache important?
You mean the cache on the HDD? For backup use, not really. You're essentially writing lots of different data once in a session, without re-reading anything.
I know people who work in radio, music, etc and HDDs and BD is still the way they archive their important material. BD for in house access, and HDDs in off-site storage servers.
I have additional BD-R backups for critical data. Yes, there are some junk media out there (especially "LTH" discs), and I've had "coasters" on all CD/DVD/BD optical types, but I also have +15 year old old CD-R & DVD-R's that are still readable today. If you're going that route : Buy a 25x spindle HTL premium brands BD-R (I use Panasonic), verify after burn, avoid dual-layer media, store in jewel cases or spindles (not paper sleeves or those "100+ CD wallets" that start to bend discs) then keep them in a dark place with little temperature variation (indoor cupboard, not an unheated garage), and they can last decades. Biggest frustration is burning a large media collection with them (500GB data = around 22x discs). OTOH, for unchanging data it only needs to be done once and the media is then separate from the reading drive.
Other advice: when backing up files, use some form of CRC compare utility to make sure it's been stored properly. I use
Teracopy (free) and it's great. Does CRC check on source file whilst copying, then flushes cache / buffer, then reads back destination file and compares them. It can eliminate the possibility of "silent errors" (eg, faulty SATA / USB cables causing bit errors which don't always show up in Windows).