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

On 6/23/26 22:39, [email protected] wrote:
> On Tue, Jun 23, 2026 at 03:04:38PM -0700, David Christensen wrote:
>> I was thinking of what happens if a disk fails, the sysadmin disposes of the
>> disk, an attacker obtains the disk, and the attacker successfully cracks the
>> encryption.  The attacker now has all or part of the plaintext data, the
>> plaintext metadata, and the plaintext cryptographic details at the time the
>> disk failed:
> 
> Never do that. If the electronics still work to dd to the first sectors
> of the disk, by all means, do.


Using software to write zeroes to a drive will get the sectors that the 
drive controller allows the host to see, but HDD failed/ remapped 
sectors will still contain content; as will dirty SSD/ USB flash sectors 
waiting to be erased.  If a skilled attacker obtains the drive at this 
point, the remaining data could be compromised.


ATA Secure Erase is supposed to get more (all?) sectors, but I do not 
know what happens with broken sectors.


I have heard of people using magnetic erasers for magnetic HDD's.


I have heard of disk shredding and/or incineration services, but that is 
above my scale.


My practice has been zeroes and/or secure erase, followed by a 3 pound 
drilling hammer.


David