Tape vs disk cost

[Mark J Dulcey]

On 3/28/2010 9:45 PM, Jack-rp9/bkPP+cDYtjvyW6yDsg at public.gmane.org wrote:
> Long term stability of tapes is also an issue.   LTO's have a timing
> track pre-recorded, so it
> should help.   Sofar I haven't found any really good archive media
> (like rock-stable 50 year life)
> that has any reasonable access time and cost per unit, including r/w device.

My point was not that tape has no issues -- I know it does. But at least 
they're reasonably well known from years of experience. I don't know if 
anybody really knows what happens to hard drives that are shelved for 
years; the closest thing would be the track record of removable disk 
cartridges, which used to be popular once upon a time. And the 
technology of nearly all of them is so radically different from modern 
hard disks that it likely doesn't mean much.

> The current best I have found for large amounts of data is tape (in
> some reasonably current form),
> or 'archival DVD's.

The problem with DVDs is that their capacity is so small compared to the 
size of modern hard disks that it takes a ridiculous number of them to 
do a full backup. Do you have the patience to create a FOUR HUNDRED DISC 
backup set for your 2TB hard drive?, Oh, alright, if you use dual layer 
discs you'll only need 250 of them. (Numbers rounded but you get the 
idea.) BD-R would be somewhat better but it hasn't been around long 
enough to say whether it will be useful for archiving.

I do expect that we'll see at least one more generation of optical disc 
technology. The television industry is busy working on "4K" technology 
(there are already cameras that record at that resolution being used for 
digital movie making) -- in other words, televisions with about double 
the pixel count in each direction compared to 1080p. Combined with 3D, 
the current 50GB Blu-Ray discs won't be up to the task, so we'll see 
some future disc standard (likely a Blu-Ray variant with more layers 
and/or higher pit density; such discs have already been demonstrated). 
But whether we'll see a computer version, and at what price, remains to 
be seen.