Excellent link. Thanks!
Just to be pedantic, I would point out that RAID doesn't necessarily mean "safe back-up". While Patterson-Gibson-Katz (1987) RAID stands for "Redundant Array of Independent Disks", the specification can alter quite dramatically. RAID5 can restore information when a single drive out of a set has failed, but RAID0 (or striping) is a speed enhancement, not a data security standard. I mention this because a lot of PCs have SSDs in RAID0 configuration for turbo boosting. And it is confusing. So … your gaming experience is archiving games? :P

With the added task of testing the back-ups, you must spend a considerable fraction of your IT budget (money and especially time) archiving everything, then testing the files (restoring the files and running them), etc. Or are you just assuming that the backups will all work if/when they're needed? How often do you test the different media streams?
Don't get me wrong, I'm as paranoid as my budget will allow. :)
I would caution everyone concerned (i.e., those reading this thread) to check your back-ups actually will restore the content in the manner you expect. (Just like the post-write CRC checks on optical discs, for example.)
Only because I have been burnt when trying to restore a back-up. More than once. On an enterprise configuration.

Yes, that is an important point. I use e.g. rhash and/or dvdsig to check that my archives of important files are intact. It means that from time to time I e.g. run rhash verification for my whole 3TB backup drive. If I'd notice any anomaly, then I'd check the affected file(s), and copy the uncorrupted files from another 3TB drive which is a 1:1 copy of the master drive.

Yes it would be theoretically possible that the same file would have become corrupted on both drives, but I consider that so unlikely event for now that I am sticking to this. Of course none of the files on my archives are vital that I couldn't live without, mainly stuff that:

- has sentimental value to me (e.g. old VHS home videos I've moved to digital format, or old photos)

- has some monetary value to me (e.g. my DotEmu game collection; it would cost me money to rebuy them on e.g. GOG.com, and some of them are not even available on other stores)

- would inconvenience me somehow, like having to get certain data from somewhere

GOG games, at this point, are not stuff that I keep multiple backups. I have single copies of all my purchased GOG games on hard drives, but at this point I consider the GOG servers to be my backups. If I notice some GOG game installer is corrupted, I redownload it from GOG servers.

I can't do the same with e.g. my DotEmu games as DotEmu closed its store and doesn't let me redownload them anymore, so I do have two copies of my DotEmu games, for example.

About wasting time to check or verify your archives: I can simply give a command to e.g. rhash or dvdsig to do its stuff (e.g. verify all the files' integrity on my 3TB hard drive), and I can let it do its stuff on the background while I use the computer for something else. So in that sense it is not really wasting my time. The only thing I can't do is to either shut down or reboot the machine, but otherwise I hardly even notice it is doing the verification in the background. So it is not like having to manually check each and every file myself, whether they are still ok.

That is another reason why I am opposed to using optical discs for backups. If I have e.g. hundreds of old CD-R and DVD-R discs, then I would have to check them one by one, whether they are still ok, as opposed to checking only one big hard drive.

The other reason is that I don't find burned optical media secure, as I've noticed myself that a good portion of my old CD-R discs have become unreadable over time (when I finally did try to get the files from them). They were ok back when I burned them (I verified them back then), but not anymore. And yes that has happened even with more expensive, good quality CD-R and DVD-R discs, and I have kept the discs in an optimal place (dry, cool, dark place; hey that's Finland for you!).

Thanks and +1 for an excellent post with some really useful information.

Thanks also to everyone else in the thread as it's always good to get differing input on subjects like this.

I still don't understand where that information about flash storage not being good for long-time archiving really comes from. When I google for it, the information I get is that:

- flash storage (e.g. a mere USB memory stick) WILL keep your data intact for a very long time, even for decades in optimal conditions.

- however, flash memory does have an issue if you keep rewriting stuff into them. They have a limited amount of life for writing stuff to them.

So that leads me to think that for "archive and forget" type of archiving, flash memory is secure. Its problems are if you rewrite or change the data constantly, and the fact that it costs a lot per gigabyte (compared to e.g. HDDs).

Here's the earlier discussion about the subject, with some links:

https://www.gog.com/forum/general/all_my_games_in_one_place_interesting_steam_vs_gog_discussion_in_rgames/post22

So no idea if the people behind the links don't have a faintest idea what they are talking about, and flash memory sitting in your cup board will lose its data over years. I am pretty sure I have some old USB flash memory sticks in my cupboard that I haven't used for many years, maybe I should check if they really have become empty or whether the files in them are still ok. I think I have earlier checked some old memory stick I haven't used for ages, and the files were ok at least back then.

To be honest I hadn't heard that about flash storage before. I've just had a quick google and there seems to be little or no fact based consensus on the matter. However, there do seem to be sufficient concerns about possible data loss caused by long periods without power, that personally I wouldn't consider using them as a long-term 'write and forget' storage option. Then again I don't think there is any medium that I'd trust as a 'write and forget' storage option on its own.

^ That's simply not true. Example slide from JEDEC showing "guaranteed" unpowered retention that can not only be measured to be significantly less than "a very long time" but can vary according to storage temperature.

I've seen several flash drives unplugged for years whose data has been corrupt / completely blank. Not just the data but FAT file system even partition table. Ironically, it's more likely to happen to newer drives as time goes on more than older ones as the older ones used larger process nodes / MLC whilst newer ones use smaller nodes / TLC. Likewise, people do plug them in regularly which isn't the same thing as being 100% unpowered.

Basically the issue is this - flash works by storing an electric charge in a series of cells. This charge can leak out causing one voltage state to drift into the one below it. Larger sized cells (eg, 25, 32, 40nm) have lots of atoms storing the charge whilst smaller ones (16nm, etc) have fewer. Likewise MLC vs TLC stores data not just in pure 0's and 1's but in intermediate voltage states. Each one has decreasing "gap" between each voltage state shrinks:-

SLC - 100% voltage vs 0v. The cell stores things as pure 0's and 1's and a 1 would have to leak all the way down to almost nothing to become an unintended 0.

MLC - 100% / 67% / 33% / 0v. Each cell stores data as 4 potential different voltages and now a cell only has to lose 33% voltage for a "1" to drop down into the next state

TLC - 100% / 86% / 71% / 57% / 43% / 29% / 14% / 0v. Each cell stores data as 8 potential different voltages and now a cell only has to lose 14% voltage for a "1" to drop down into the next state. Even at 16nm TLC, a cell basically has only 3x atoms per voltage state holding the charge.

QLC - 100% / 93% / 87% / 80% / 73% / 67% / 60% / 53% / 47% / 40% / 33% / 27% / 20% / 13% / 7% / 0v. Each cell stores data as 16 potential different voltages and now a cell only has to lose just 7% voltage for a "1" to drop down into the next state.

You might want to Google "Samsung 840 slowdown" and read the problems there that were caused by the SSD not constantly rewriting old "stale" data to compensate for cell leakage (that turned out to be worse than Samsung originally anticipated). They slowed right down to as little as 1MB/s in some cases as the SSD's controller was frantically trying to "guestimate" back what it wrote under several layers of error correction due to voltage drift. Other SSD's have experienced the same issue. Example read speed slowdown for the Crucial BX200 which suffered the same thing after just 8 weeks.

Samsung's never actually "fixed" it, they just created a workaround where new firmware constantly rewrote the data more aggressively to stop it corrupting. Newer 3D-NAND 850 series drives went back to larger 40nm cells for a reason - it has more "insurance" against voltage drift. There have also been reports of laptop shipped with cheap TLC SSD's sitting unsold and powered off with the battery detached for several months after production, subsequently failing to boot due to the SSD losing charge and struggling to read back even the partition table / file system / Flash Translation Layer.

It's certainly not common as most people buy SSD's to use as performance system drives that are regularly powered up (plus they still make no sense for backups vs 6-10x cheaper HDD's where performance isn't a factor), but flash absolutely does leak out and this can certainly corrupt data over time if left 100% unpowered for long periods of time. It's useful for regular / occasional use, but has long been know to be unsuitable as a 100% offline / unpowered "cold storage" archival medium.

i keep a couple of large usb drives with my games backed up to both. i probably should look into a raid setup of somesuch considering the size of my gog account. it'd be a much cleaner process than doing the crap i do now.

Has anyone looked into those M-Disc Blurays? I guess the "1000 years durability" thing is mostly marketing talk, but the process itself seems rather solid. 100GB max probably isn't very practical for game or media backups but i was thinking about buying a Burner and a few of those for critical stuff, as an extra backup...

Well, stone etchings have been known to last for several thousand years if kept in decent conditions, but I guess what you are looking for are at least 2 mirrored regular (as in magnetic) external hard drives. You don't have to use anything fancy for mirroring, I just have a "master copy" which I regularly update and sync to the "backup copy" every month or so.