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Comment by lampe3 | Hacker News Reader

And why not save it on a External HDD ? I thought that CDs/DVDs are bad for backup because they crumble.

Hard disks are also bad for backup because they rely on a magnetic charge being retained on the platters. Eventually, this charge becomes to weak to be read reliably, so it is unsuitable for long-term storage. Pressed disks (as in, those not burnt with a consumer drive) can last a lifetime if you take proper care of them, and are not as vulnerable to light, heat or humidity as the typical DVD-R.

Thanks for the information.

If i cant afford to press the disks how should i backup my data?

Right now we are using nas systems with a raid setup

LTO tape or Taiyo Yuden CD-Rs are my recommendations and what I personally use at home. And I haven't checked for a few years to see if Taiyo Yuden is still producing good stuff, but if you're paying around 25 cents per disc it probably still is. MAM-A CD-R media is probably a good bet; I don't recommend DVD recordable media, even MAM-A Gold, because it pushed CD-R technology too far.

Per sspiff, you do need to protect optical media from environmental extremes. Tape cartridges are more physically fragile (although I'm sure there's data recovery firms that'll repack the tape into a new cartridge) and also shouldn't get too hot or humid. And ideally are stacked on edge.

To be honest, I haven't got a clue. Affordable, multi-decade storage is still an unsolved problem as far as I know.

A RAID NAS is a good medium-term solution, and perhaps creating offline backups on disconnected drives every 5 years or so can solve long term storage, though it does require maintenance over time (refreshing the drives). If you are not afraid to use cloud storage, you might use those services, but I don't know how long those will be around.

Note that if you're using cheap, big consumer quality disks and RAID 5, if you lose one you're likely to lose the whole array because at least one of the other disks will have unrecoverable read errors during the rebuild. RAID 6 helps, but the math is still frightening.

Granted, I haven't looked for years at what's been done to address this, but based on the state of the art back then I'd only try this with ZFS, which checksums everything it puts to disk, which among other things catches the incredible screw case of the very complicated firmware writing the right data correctly to the wrong location on the disk (!).

Any idea how much it costs to have a disc pressed? For some things of mine it might be worth it.

Harddisks (magnetic storage) are very poor for long-term storage. Especially modern 2TB+ ones. If you saw the raw error rates (that get repaired using checksums) on a typical drive you'd be very afraid.

Thank you for the information.

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