[TriLUG] Bit rot detection without ZFS/btrfs?

[Steve Holton]

At this point, one risks becoming a veterinarian for Schrödinger's cat: any
bit not currently being observed is neither valid nor rotten.

Use an error-correcting (RAID 5) for the source.
Make on-site backups against catastrophic failure, and just *trust* they
will be good. (if catastrophe occurs, but one refuses to trust one's
on-site backups until one knows they match the off-sites, what's the point
of having an on-site? And if there *is* a mismatch???)

If you absolutely must minimize the risk of bit rot in a backup, you'll
need to minimize the *space-time* (no technobabble intended) between
observations: adding either time between observations or distance between
the source and backup will increase risk.





On Tue, Jul 2, 2013 at 10:15 AM, Randy Barlow
<randy at electronsweatshop.com>wrote:

> On Mon, 01 Jul 2013 15:40:20 -0400, Steve Holton <sph0lt0n at gmail.com>
> wrote:
>
>> But what happens if there's bit-rot on the destination machine....
>>
>
> In the tentative plans for what I intend to do, there will be at least
> three copies of all my files. One on the source, one on the backup system,
> and one on the offsite backup system.
>
> If all three places checksum the files, then if any one of them reports a
> mismatch, you can use the other two to determine whether it was the
> checksum that rotted (since the checksum itself could be wrong), or the
> file. Then corrective action can be taken.
>
> --
> R
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-- 
-- 
Steve Holton
sph0lt0n at gmail.com