Tape vs disk cost

[Mark J Dulcey]

On 3/29/2010 7:44 AM, Edward Ned Harvey wrote:

> Everytime I re-examine this, roughly speaking, the breakeven point is approx
> 10 disks or tapes.  More than that, tapes are cheaper.  Less than that,
> disks are cheaper.

The math I posted earlier comes out a bit differently. The current 
breakeven is at 35+ bare hard disks (or almost 90 tapes since they hold 
less) or 25+ hard disks in cheap cases (over 60 tapes). Double those 
numbers if you want a second tape drive as a backup. This is all based 
on using 2TB hard drives, which have recently become cost effective.

So... tape remains attractive for big data centers, especially ones that 
have to keep multiple generations of backups for legal reasons. But at 
least on the numbers, external hard disks look like the winner for 
individuals and small businesses, perhaps combined with online backup as 
a second line of defense.

An alternative is redundant storage of data on multiple live systems. 
That's Google's main line of defense. In a typical home scenario you may 
have some data on multiple systems (so less need for tape/disk backups), 
some that is only on one (the critical stuff to back up), and some that 
you don't care about backing up at all (downloaded software install 
files for example, since they'll usually be out of date by the time you 
need them). So design your backup strategy to balance your cost and time 
budget for backup against your paranoia level for your data.