Dell UCP-60, UCP-61, UCC-60 manual Caching, 137

Caching

The process of utilizing a high speed memory buffer, referred to as a “cache,” in order to speed up the overall read or write performance. This cache can be accessed at a higher speed than a disk subsystem. To improve read performance, the cache usually contains the most recently accessed data, as well as data from adjacent disk sectors. To improve write performance, the cache may temporarily store data in accordance with its write back policies. See the definition of Write-Backfor more information.

Consistency Check

An operation to verify that all stripes in a virtual disk with a redundant RAID level are consistent and automatically fix any errors. For RAID 5, 6, 50, and 60 arrays, consistency check verifies correct parity data for each stripe. For RAID 1 and RAID 10 arrays, this operation verifies correct mirror data for each stripe.

Controller

A chip that controls the transfer of data between the microprocessor and memory or between the microprocessor and a peripheral device such as a physical disk or the keyboard. In Storage Management, the hardware or logic that interacts with storage devices to write and retrieve data and perform storage management. RAID controllers perform RAID functions such as striping and mirroring to provide data protection.

D

DDR SDRAM

Acronym for Double Data Rate Synchronous Dynamic Random Access Memory. This is a type of SDRAM that provides data throughput at double the rate of conventional SDRAM. It uses a bursting technique to predict the address of the next memory location to be accessed and allows two data transfers on each clock cycle.

Disk

A non-volatile, randomly addressable, rewriteable mass storage device, including both rotating magnetic and optical storage devices and solid-state storage devices, or non-volatile electronic storage elements.

Glossary

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