With the recent deployments of high-capacity low-cost drives (such as SATA), the cost benefit ratios are now closer to 4:1 in favor of tape. Tape has historically been approximately eight or 10 times less expensive than disk storage to acquire and operate.

However, operational costs shouldn't be overlooked.

Organizations often use only hard accounting costs because of to the relative ease in calculating these costs. The RPO is the amount of data that may be lost, and the RTO is the amount of time it takes to perform the recovery. The SLA metrics must be specified by the business application owners and should include the recovery point objective (RPO) and the recovery time objective (RTO).

What are the costs for delayed processing (data not lost, although application isn't running for some time) on a per hour basis?.

What are the costs for lost data per hour for the applications that are being protected?.

To determine the value of data, answer the following questions: The cost to a company such as Amazon, American Express, eBay or Visa may be on the order of several million dollars per hour. The lost business opportunity due to a website outage for a small law firm may be inconsequential. The value of data varies significantly among industries, the size of the company and even by an application within the same firm. Disk storage typically isn't less expensive than tape, but it can be the best way to deliver to meet a service-level agreement (SLA).

Cost of one drive