 - A hard disk is part of a unit, often called a "disk drive," "hard drive," or "hard disk drive," that stores and provides relatively quick access to large amounts of data on an electromagnetically charged surface or set of surfaces. Today's computers typically come with a hard disk that contains several billion bytes (gigabytes) of storage.
A hard disk is really a set of stacked "disks," each of which, like phonograph records, has data recorded electromagnetically in concentric circles or "tracks" on the disk. A "head" (something like a phonograph arm but in a relatively fixed position) records (writes) or reads the information on the tracks. Two heads, one on each side of a disk, read or write the data as the disk spins. Each read or write operation requires that data be located, which is an operation called a "seek." (Data already in a disk cache, however, will be located more quickly.)
A hard disk/drive unit comes with a set rotation speed varying from 4500 to 7200 rpm. Disk access time is measured in milliseconds. Although the physical location can be identified with cylinder, track, and sector locations, these are actually mapped to a logical block address (LBA) that works with the larger address range on today's hard disks.
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Learn more about Disk arrays |
| No-maintenance disk array aims to eliminate hard drive swapping: SAID (Sealed Array of Identical Disks) array from startup Atrato bridges the performance-capacity gap. It can in theory run for the term of a 5-year lease with zero maintenance. |
| Fail-in-place systems: Avoiding hard disk drive failures: Fail-in-place storage systems, such Atrato's V1000 and Xiotech's Emprise 5000 or ISE, can virtually eliminate hard disk drive replacement service calls. |
| Multiprotocol storage arrays gain interest, adoption: Multiprotocol storage arrays, or unified storage, combine block and file storage access protocols. Interest due to cost savings, advances in technology and simpler management. |
| Enterprise disk array consolidation product specifications: Knowing the purchasing criteria for enterprise-class disk arrays, as well as product specs for the leading arrays, can help storage managers make savvy buying decisions. |
| What is a terabyte? What is bigger than a terabyte?: What is a terabyte? What are terabytes? What are terabyte drives? What comes after a terabyte? What's bigger than a terabyte? Please don't just say that 2 terabytes is bigger than one terabyte. |
| Storwize claims good data compression rates, no performance degradation on STN-6000 appliance: Storwize's STN-6000 inline appliance acts on primary storage using real-time compression. |
| NetApp: Post-process deduplication limits performance hit in primary storage data deduplication: NetApp's approach to primary storage data deduplication limits the performance penalty to about 20% percent. |
| Best practices for solid-state drive storage technology: SSD best practices center on identifying I/O-intensive applications so that data storage technology can provide the greatest benefit to IT organizations. |
| Storage arrays quiz: Take our quiz and become a scholar on storage arrays, including array-based memory, RAID, and storage consolidation. |
| Podcast: Solid-state drives entering enterprise storage environments: Jeff Janukowicz, research manager at IDC for solid-state drives and hard drive components, discusses the impact SSDs are expected to have at the enterprise level. |
| LAST UPDATED: |
18 Feb 2004
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RELATED GLOSSARY TERMS
| Terms from Whatis.com − the technology online dictionary |
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array
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In general, an array is a number of items arranged in some specified way - for example, in a list or in a three-dimensional table.
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array-based memory
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Array-based memory is an evolving solid-state storage technology similar to flash memory but with potentially greater storage capacity. The increased...
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