Ed Wilts said:

>1)  Disk ages and breaks too.  

But with RAID, no longer will the failure of a piece of media cause a
backup or restore failure.

>2)  Transport is cheap.  I'd be surprised if I couldn't transport a
>thousand tapes for the cost of a terabyte of storage.  Bandwidth to
move >data is *NOT* cheap.  20GB/day requires 3Mbps of pipe.

I've done a number of cost comparisons lately, and you're right.  It's
not cheap, but it's not astronomical either.  And you need to weigh that
cost against not having the risk of a lost tape and all the
multi-million dollar costs that come along with that these days.

>3)  I spend more time replacing disk drives than I do replacing tapes
or
>tape drives.   To back up my 1200 SAN-based spindles, I have 6 LTO-3
drives.

You have 200 times more disk drives than you have tape drives.  Of
course you spend more time replacing them.  But those drive failures
never have to cause backup or restore failures, as tape/drive failures
do.  Try having a few hundred tape drives and see how your life changes.
I have a customer with 100 drives and their tape drive vendor is in once
a week swapping something, and each one of those swaps is associated
with a backup or restore failure.


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