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There is one question which is bothering me alot: It is said that data can only be held on magnetic disks for about 5 years. After that, it could get lost because the magnetic force on the disk gets "weak" (I do not really know how to describe it better ;))

Do disks counteract against this? For example: Do they rewrite all their bits from time to time when they are idling?

Regards Christian

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  • Some RAID cards to 'patrol reads' where they use idle time to read all data. If that reading fails action can be taken. No idea if, or how this is implemented in normal disks firmware or in drivers.
    – Hennes
    Commented Sep 25, 2015 at 13:37
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    This is a nice question, but it is a possible duplicate of How much time until an unused hard drive loses its data?
    – Deltik
    Commented Sep 25, 2015 at 13:40
  • I've been travelling for a few years - my fileserver back home powers on periodically and 'dd'-reads every disk to /dev/null for the problem you describe. So far, no data loss or errors reported :)
    – Mark K Cowan
    Commented Sep 27, 2015 at 8:31

2 Answers 2

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Writing to a disk takes time and a disk will wear from excessive writing. Although with an SSD this is much more troublesome than with a harddisk, it still happens.

So to answer your question, no a harddisk does not rewrites itself to maintain coherence.

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No, being in computer science for more than 20 years I never heard about such a mechanism.

However it is uncommon that a hard disk driver is used this long.

(also Disk de-fragmentation process rewrite (move) part of the data but not all)

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