Re: How to salvage a degraded mdadm RAID1 with as little data loss as possible?

On Sat, Jun 20, 2026 at 09:47:23PM -0700, David Christensen wrote:

[...]

> That is also my understanding.  The HDD's I own are proprietary, so the
> engineering documentation is unavailable.  But, I seem to recall reading an
> article on the WWW stating that HDD's store additional data in hidden blocks
> on the media to allow detecting and/or correcting several flipped bits.

Much more than that. They do accept some error rate which is corrected
(it has long been an engineering tradeoff: more density -> higher error
rate -> better error correction codes):

  "For example, a typical 1 TB hard disk with 512-byte sectors provides
  additional capacity of about 93 GB for the ECC data."

From: https://en.wikipedia.org/wiki/Hard_disk#Error_rates_and_handling

Wikipedia: better than "the WWW". Especially in these times.

Cheers
-- 
t

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