Tape Storage vs. Disk Storage: Getting the Facts Straight about Total Cost of Ownership Calculations
Modern tape storage has long been recognized for its low cost. Several analyst white papers have been published that demonstrate the low cost of storing data on tape. For example, “Quantifying the Economic Benefits of LTO-8 Technology” is a white paper that can be found on the LTO.org website. However, occasionally a storage solution provider publishes a white paper that claims to show that their solution is less expensive than tape storage for a particular use case. A good example is a recent white paper published by a disk-based backup-as-a-service provider who will remain unidentified out of respect for what they do. For the purpose of this blog, let’s call them “BaaS.” So let’s dig into their analysis which makes several assumptions that result in higher costs for tape storage than most users would experience.
Total Cost of Ownership (TCO) Process
The first step in developing a Total Cost of Ownership (TCO) estimate is the determination of the amount of data to be stored. The BaaS whitepaper separates the amount of primary data, which we wish to protect, from backup data, which is the data physically stored on the backup media. They estimate the amount of backup data residing in the tape library to be two to four times the primary data. This is due to their use of the old daily/ weekly/monthly/ full backup methodology for estimating the amount of backup data. The result is that two to four times the amount of primary data ends up being stored on tape, raising the tape hardware and media costs by two to four times.