Cost Comparisons: Centralized Data Storage -vs- Local

[dal.mobil.com">jemartin]

We have recently begun using our mass storage platform for near-
line storage of workstation and server data.  Our users are
balking at the charges incurred because, they say, they can purchase
new disks at a fraction of what we are asking for our services.

I have been asked to help develop a cost comparison in terms 
of $$/Mb between server disk storage and high density tape storage 
from the user perspective. If services are provided from a centralized 
entity (i.e., our organization), their charges represent this cost.  
If services are obtained locally, all costs such as hardware, support,
maintenance, and backup should be included.  

Specifically, I'd like to compare between a centralized mass
storage facility vs. disk the users claim they can buy for their
server and store their own data for less cost per Mb.

Since charge rates for disk usually include a time factor (i.e.,
$$/Mb/day), how can data storage rates between disk and tape
(infinite time storage) be fairly compared??

I'm curious as to whether or not anybody else has done anything
similar.  Also, what factors should we consider that I may have 
overlooked.    


             I would appreciate any input you may provide,

                                Jose' Martinez

                                     | jemartindal.mobil.com
                                     | J.E. Martinez, Sr. Comp Sup Tech
                                     | MEPTEC IT/CS&S, Dallas TX
                                     | (214) 951-3514
                                     | FAX (214) 951-3529