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One thing that keeps me from trying tapes is that they are still magnetic. If there's some sort of local electromagnetic event then I'd prefer to have a backup

One thing that keeps me from trying tapes is that they are still magnetic. If there's some sort of local electromagnetic event then I'd prefer to have a backup that can handle that. I keep some backup hard drives in metal boxes, which is probably enough (Faraday cage). However, optical disks can almost certainly survive a major electromagnetic event without special precautions.

uniqueuid 5y ago
Interesting. Is a magnetic event more plausible for you than other types of decay? I'd expect physical damage from something like a flooding to be much more likely than some sort of magnetic interference. But that probably depends on the location you live in!
- wtetzner 5y ago
  I think the idea is just to have different kinds of backups that have different failure modes, to make losing everything at once less likely.
- btrettel 5y ago
  I don't know how likely some sort of electromagnetic event is. I just figure that if I'm going to diversify my backup strategies then something dissimilar/uncorrelated would probably be a better choice. My data is on magnetic hard drives, SSDs, and optical disks, each of which has different risk profiles. As wtetzner said, it's unlikely that a single event could cause all of these to fail. An EMP attack might take out my magnetic hard drives and SSDs but leave the optical disks unaffected. I've also had a hard drive fail due to impact damage that likely would not affect a SSD. Flooding is not something I've thought about before, but since my backups are located in different geographical areas, I should be covered there. Etc.
axiolite 5y ago
> local electromagnetic event then I'd prefer to have a backup that can handle that. First of all, the magnetic gauss needed to flip bits on LTO media is huge. It's not a practical concern unless you're choosing an incredibly inappropriate storage location. Second, why wouldn't you store your tapes in a case or a vault that is magnetically shielded? You probably store your discs in cases, instead of insisting they be naturally durable against rough handling and abrasion.
- btrettel 5y ago
  > First of all, the magnetic gauss needed to flip bits on LTO media is huge. It's not a practical concern unless you're choosing an incredibly inappropriate storage location. You're right, it does seem huge: https://superuser.com/a/568367/111650 https://superuser.com/a/568367/111650 (Some of the links from this answer are quite interesting.) The issue is that I don't know (and I suspect it's difficult to know or even classified) whether an EMP attack (the main scenario I'm worried about, which can be quite powerful) would be sufficient to cause damage. I don't believe there is a consensus on this though I'd be glad to be proved wrong here. > why wouldn't you store your tapes in a case or a vault that is magnetically shielded? I would; as I said I put some magnetic hard drives in Faraday cages. However, I'm not confident that the Faraday cage would be sufficient. A lot of the discussion online about constructing Faraday cages to protect electronics is speculation. I haven't seen any clear data showing that during an EMP attack magnetic data is protected inside of a Faraday cage, or protected without one.
  - axiolite 5y ago
    > I'm not confident that the Faraday cage would be sufficient. Faraday cages are not intended for that purpose. Magnetic shielding is a well understood concept. What you need is some thickness of ferrous metals. https://en.wikipedia.org/wiki/Electromagnetic_shielding#Magnetic_shielding https://en.wikipedia.org/wiki/Electromagnetic_shielding#Magn... https://web.archive.org/web/20070327130322/https://advancemag.com/needfor.htm https://web.archive.org/web/20070327130322/https://advancema... https://interferencetechnology.com/magnetic-shielding-basics/ https://interferencetechnology.com/magnetic-shielding-basics... It's easy to test the efficacy of magnetic shielding yourself if you have a large, powerful magnet and a CRT monitor handy.
    - btrettel 5y ago
      Noted, thank you much.
  - PaulHoule 5y ago
    The EMP from a nuclear weapon is mostly radio frequency and would be picked up by antennas, power lines and such. (I know an ex-military ham who always unplugs his HF/shortwave radio from the antenna and power when he's not using it because that's what they taught him to do back in the day.) I don't see that kind of EMP erasing magnetic media.

uniqueuid 5y ago

Interesting. Is a magnetic event more plausible for you than other types of decay? I'd expect physical damage from something like a flooding to be much more likely than some sort of magnetic interference. But that probably depends on the location you live in!

wtetzner 5y ago
I think the idea is just to have different kinds of backups that have different failure modes, to make losing everything at once less likely.
btrettel 5y ago
I don't know how likely some sort of electromagnetic event is. I just figure that if I'm going to diversify my backup strategies then something dissimilar/uncorrelated would probably be a better choice. My data is on magnetic hard drives, SSDs, and optical disks, each of which has different risk profiles. As wtetzner said, it's unlikely that a single event could cause all of these to fail. An EMP attack might take out my magnetic hard drives and SSDs but leave the optical disks unaffected. I've also had a hard drive fail due to impact damage that likely would not affect a SSD. Flooding is not something I've thought about before, but since my backups are located in different geographical areas, I should be covered there. Etc.

axiolite 5y ago

> local electromagnetic event then I'd prefer to have a backup that can handle that. First of all, the magnetic gauss needed to flip bits on LTO media is huge. It's not a practical concern unless you're choosing an incredibly inappropriate storage location. Second, why wouldn't you store your tapes in a case or a vault that is magnetically shielded? You probably store your discs in cases, instead of insisting they be naturally durable against rough handling and abrasion.

btrettel 5y ago
> First of all, the magnetic gauss needed to flip bits on LTO media is huge. It's not a practical concern unless you're choosing an incredibly inappropriate storage location. You're right, it does seem huge: https://superuser.com/a/568367/111650 https://superuser.com/a/568367/111650 (Some of the links from this answer are quite interesting.) The issue is that I don't know (and I suspect it's difficult to know or even classified) whether an EMP attack (the main scenario I'm worried about, which can be quite powerful) would be sufficient to cause damage. I don't believe there is a consensus on this though I'd be glad to be proved wrong here. > why wouldn't you store your tapes in a case or a vault that is magnetically shielded? I would; as I said I put some magnetic hard drives in Faraday cages. However, I'm not confident that the Faraday cage would be sufficient. A lot of the discussion online about constructing Faraday cages to protect electronics is speculation. I haven't seen any clear data showing that during an EMP attack magnetic data is protected inside of a Faraday cage, or protected without one.
- axiolite 5y ago
  > I'm not confident that the Faraday cage would be sufficient. Faraday cages are not intended for that purpose. Magnetic shielding is a well understood concept. What you need is some thickness of ferrous metals. https://en.wikipedia.org/wiki/Electromagnetic_shielding#Magnetic_shielding https://en.wikipedia.org/wiki/Electromagnetic_shielding#Magn... https://web.archive.org/web/20070327130322/https://advancemag.com/needfor.htm https://web.archive.org/web/20070327130322/https://advancema... https://interferencetechnology.com/magnetic-shielding-basics/ https://interferencetechnology.com/magnetic-shielding-basics... It's easy to test the efficacy of magnetic shielding yourself if you have a large, powerful magnet and a CRT monitor handy.
  - btrettel 5y ago
    Noted, thank you much.
- PaulHoule 5y ago
  The EMP from a nuclear weapon is mostly radio frequency and would be picked up by antennas, power lines and such. (I know an ex-military ham who always unplugs his HF/shortwave radio from the antenna and power when he's not using it because that's what they taught him to do back in the day.) I don't see that kind of EMP erasing magnetic media.