"bitrot" on magnetic media: is there such a thing?

[charles at c3pe.UUCP]

In article <826 at PUCC.BITNET> D0430 at PUCC.BITNET writes:
>In article <147 at itcatl.UUCP>, robin at itcatl.UUCP (Robin Cutshaw) writes:
>>I have been getting numerous soft errors on the G partition
>>and a few hard errors there.
> 
>We had the same problem with an rd53, lots of soft errors, turning into
>hard errors, running rabads every day to replace it, etc.  We finally
>just reformatted the disk and all the problems vanished.

That raises an interesting question:  I've noticed a similar phenomenon with
certain 5.25" Winchesters.  In our case (Xenix), reformatting destroys special
"bad sector" flags in the address fields of bad blocks.  These are used to
construct a map later used by the kernel to make all partitions appear "clean";
if one reformats the disk without noting previously-bad sectors, they may come
back to bite later.  Thus, I'm reluctant to tell someone to reformat their disk
unless they're getting "Address Not Found" errors.

But I'm beginning to wonder:  after the address marks are written on a disk
during formatting, as the years go by, do they gradually "entrophy"
(atrophy via entropy!), or melt into the noise?
-- 
_____-__---__-_----_-__-_-_----__-_--_--___-_---__-__-_-_-_--__-_-__--___-_____
-Charles Green at C3 Inc.	{{styx!seismo,cvl}!decuac,dolqci}!c3pe!charles
You hear the howling of the Winchester. The voltage spike hits! You crash.-More