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The Tiered Storage Hierarchy
Since 1956, when the first disk and tape drives originally defined the storage hierarchy, a pyramid or triangle has been used to depict a tiered hierarchy of products spanning all levels of price, performance and capacities. Driven by growing amounts of fixed content, compliance and archival data, implementing a storage hierarchy can result in significant infrastructure savings. Broad ranges exist within the hierarchy and some unfilled price, performance and capacity gaps are finally closing as integrated tape libraries combined with virtual disk arrays along with the emerging economy SATA-based disk storage category is rapidly expanding.
SSD (solid-state disk) provides the highest I/O performance of any storage device and consists of DRAM chip technology for data storage. In the future, SSDs will likely implement flash memories to reduce cost and eliminate volatility concerns. Solid-state disk removes the time-consuming latency and seek components from every I/O operation, requiring only a few microseconds access time and then the direct data transfer operation from memory. SSDs address the niche database accelerator market most effectively.
Magnetic disk contains nearly all of the world's mission-critical data, and its ultra-high reliability and availability capabilities are the primary selection factors over all other options for mission-critical data. Disk subsystems clearly store the most critical, revenue generating, highest-performance and random-access levels in the storage hierarchy.
Nearline defines the level of storage between online disk and far-line or shelved storage. Nearline storage developments have increased in the past year with several new economy disk array implementations. Several of these offerings are classified as virtual tape, and can be integrated into an automated tape library, since the disk array appears as several tape drives. In addition to still being a popular backup medium, nearline storage is the primary repository for the majority of the world's digital archives and contains an estimated 80 percent of the world's digitally stored data. Far-line, or manually retrieved media, still represents the vast majority of the world's analog or non-machine-readable data, as the fast conversion to digitization is slowing but not halting its growth rate.
Managing and exploiting the hierarchy for maximum benefit is increasingly more important and the three-tiered hierarchy has gained significant momentum in the wake of growing ILM and compliance initiatives worldwide. The robust hierarchy of storage devices that exists today, in conjunction with improved storage management software and SANs with improving intelligent, data-management capabilities, should significantly reduce the storage management burden from its current painful levels at some point in the future. As the amount of storage grows the payoff for implementing effective tiered-storage hierarchy increases dramatically.
Source: Horison Information Strategies: Storage Navigator
© 2005 Horison
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