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Our company wants to do some local (non-cloud) backup, I'm thinking the easiest is to get some high quality external hard drives, copy the data onto them, detach them, then store the drives in a climate-controlled environment. I'm imagining having two sets of drives that I alternate monthly backups.

How much "bit rot" will there be on drives that are sitting on a shelf, powered down? The lifespan of drives seems to always be given in terms of hours of actual use - and in this case that would be a very small number.

Betty Crokker
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    Good question. I think the conventional media for offline storage is still tape as that is known to last for years – HBruijn Oct 05 '19 at 19:30
  • Please describe the OS(s) in use and the backup tool/software you are going to be using, and I can edit my answer to include some options for error detection. – Rob Pearson Oct 05 '19 at 19:51
  • I'm running Windows, was thinking about just straight copying the files onto a hard disk, didn't think about error detection/correction but that's a really good idea. If you've got suggestions I'm definitely open! – Betty Crokker Oct 05 '19 at 20:14
  • @BettyCrokker - ok, I'll edit in an easy suggestion. Thank you for the information. – Rob Pearson Oct 06 '19 at 00:10

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Use tape for long-term archives and multiple public clouds (multiple tape-in-cloud still as no way anybody can store PBs of "ice cold" data on anything except tape). Hard disk isn't designed to store data for a long periods of time. 3-2-1 backup rule is in power either way.

https://www.starwindsoftware.com/blog/3-2-1-backup-strategy-why-your-data-always-survives

NISMO1968
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Disks on shelves don't last much more than spinning disks. Generally bit rot isn't a problem, however stored disks not spinning up after a few months unused is pretty common. For long term passive storage, state of the art still is either tape (LTO) or optical media.

wazoox
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This is a very interesting question without a definitive answer. On Internet you can read various answers (for example, on SuperUser or storagecraft), suggesting something on the lines of 3-10 years.

However, at best of my knowledge no real scientific study was done on this very important question (especially on modern high density PMR drives), so all answer are basically handwaving. With that premise, I would like to bring to your attention the following points:

  • HDDs are mechanical devices that rely on the properties of a specific lubrificant fluid which, if left unused, dries-up. This means that an HDD left unpowered for years can have difficulties spinning up, in (rare) extreme case even causing some voltage spikes that can "toast" other devices connected to the same power rail;

  • magnetic strength degrades at a rate of 1% each year so, theorethically, after some decades it will become much weaker. As modern HDD uses an embedded, magnetical servo track which will itself degrade but you can not rewrite, after some years the head could have issues locking the track/platter, finally losing all access to the data (NOTE: to be clear, this applies to powered disks also).

My anecdotal evidence is that some HDDs (with capacities ranging from 200-1500 GB) had no problem with >1 year of unpowered storage. On the other hand, some other drives (1 TB 2010-era low power disks) shows uncorrectable errors / pending sectors after only some weeks of unpowered storage. Obviously, as all anectodes, I know this has no statistical value.

shodanshok
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Over the span of a month or two, there should be no bit rot whatsoever. You should be able to minimize hardware failures with proper storage conditions. Depending on what you'll be using to do perform the backups, you should have an option for including error detection (and possibly correction) technology.

Since you are using Windows and don't have any special requirements, you can use the Backup and Restore tool that Windows 7 (and newer) ships with. Hit the Windows key and start typing "backup" - depending on the version of Windows you are using you may get a few different results. To use this tool, you want to find "Backup and Restore Tool". It should be pretty self-evident how to use the software once you have it open - you select the folders/drives that you want to protect, set a schedule, and set your backup destination(s).

https://lifehacker.com/how-long-can-a-hard-drive-hold-data-without-power-5808858 https://www.howtogeek.com/howto/1838/using-backup-and-restore-in-windows-7/

Rob Pearson
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  • If either of the folks who voted this down would mind commenting - I'd like to know what made this a bad answer for you. I attempted to answer the question without changing the method to something completely different (tape substituted in instead of the requested hard drives) or inappropriately complex or expensive. – Rob Pearson Oct 10 '19 at 19:32