|
Storage Pricing Guidelines
For years, tape storage was considered to be cheaper than disk storage on a per-gigabyte basis. The price per gigabyte is the capital expense (Capex) or acquisition expense. In the late 1990s, after a decade of disk price erosion exceeding 30 percent annually and relatively few technological enhancements to tape technology, the perception about disk pricing falling below tape pricing became more widespread. In the late 1990s, tape technology began to accelerate its development curve. Historically, multiple tape cartridges or reels had been required to back up the entire capacity of a disk drive. Beginning in 2002, a single tape cartridge could contain multiple copies of the largest disk. The typical high-capacity tape cartridges now have native capacities of 400 to 500 gigabytes and a compressed capacity of 800 gigabytes to 1.6 terabytes using a 2-to-1 compression ratio. The largest disk HDA announced to date has a capacity of 750 gigabytes. The price per gigabyte for all types of storage continues to fall annually, helping businesses reduce storage acquisition expenses while keeping pressure on storage suppliers to continually improve their technologies. Industry average disk pricing levels vary with the capacity of the subsystem, amount of cache, special features, status with the vendor and the level of public visibility of the account. Keep in mind that the capital expense (Capex) or acquisition expense is different from the operating expense (Opex). A low Capex doesn't usually mean a low Opex.
The key factor used to determine the purchase price per gigabyte for an automated tape library subsystem is the ratio of the number of tape cartridges to the number of tape drives in the library. The price of tape decreases as the ratio of cartridges to drives increases. Horison Information Strategies (www.horison.com) tracks storage pricing levels and average hardware selling price comparisons were made for working subsystems of enterprise-class and midrange disk, for the new Blue-laser optical libraries, economy disk subsystems and tape library subsystems. For a working tape library subsystem, point-in-time average selling prices for automated tape libraries using ultra-SCSI tape drives and 200-gigabyte native (400-gigabytes compressed) cartridges were used to determine library capacity. Non-automated (offline) tape storage is not included in the study because the cartridge-per-drive ratio is meaningless. Average selling prices for new Blue-laser optical disk libraries range from $10 to $30 per gigabyte. These comparisons do not include any storage management software or facility costs as these are optional and vary widely for each storage product category. New MAID (Massive Arrays of Idle Disks) subsystems offer the best opportunity to take market share from traditional automated tape storage as MAID brings the Capex and Opex closer to automated tape while offering superior performance characteristics.
Typical tape libraries used in non-mainframe or midrange systems average from four to as many as 20 tape drives and typically contain from 80 to 700 cartridges. These numbers are larger for mainframe tape libraries. The price per gigabyte of tape diverges from the price per gigabyte of disk as the ratio of cartridges to drives increases. The average ratio of cartridges to drives in an automated tape library can range from 20 to 80 with 15 to 40 being the most common range. For typical working automated tape configurations, the price per gigabyte of automated tape ranges from one-fourth to less than one-twentieth the price of an equivalent amount of disk storage. If cartridge capacity increases, the price per gigabyte decreases. Automated tape remains the lowest-price storage for midrange and enterprise systems, and technology roadmaps indicate that this is expected to remain so for the next eight to 10 years.
Source: Horison Information Strategies: Storage Navigator
© 2005 Horison
|
|
|
