Ann W. Harrison wrote:

>>When was shadowing first introduced in IB? Was RAID popular at the time?
>>What is the original reasoning for shadowing and what is the future of
>>shadowing?
>
> Shadowing was added in Version 2, I think, in the mid-eighties as an
> all but instant recovery system. At the time, if I recall, there had
> been a rash of disks with bad fans, some sort of adhesive that let go
> and trashed the platters, and similar problems. Though RAID hadn't
> been invented (that I know of), DEC had some fairly sophisticated disk
> management stuff with striping, shadowing, etc.
>
> There are no plans to remove shadowing from the product.

Thanks for the background story, Ann. Some google result says that RAID
was invented in the "early 80's".

Also good to hear shadowing will stay for now, since I've read that RAID
systems also screw up your data sometimes (e.g. bad controller
corrupting a good mirror, or failing to re-sync a mirror, etc.). And
things might get worse with cheap motherboards getting RAID features and
all.

--
dave