R ‐ Data Recovery Glossary R&D‐ Research and development. Radial Path– The straight‐line path from the center of the disk to the outer edge of the disk. RAID (Redundant Arrays of Independent Disks) –It is an idea in storage subsystems that can deliver enhanced protection against data loss and down‐time than conventional disk drives. RAID refers to a drive architecture that is designed to protect critical data through redundancy. In theory, conventional discs which made up the RAID arrays can function for hundred or even thousands of years without losing data because of disc failure. Other benefits of RAID include an improvement in input/output performance, allowing users to fine‐tune drive systems to match the needs of specific applications and making servicing quicker and simpler. RAM–Random Access Memory (also see DRAM, SDRAM). It is a data storage device that does not affect the speed of access as different locations are accessed. This is an anti‐thesis to the magnetic tape or magnetic disk where data access is much quicker sequentially because physical movement is required in non‐sequential location of the storage medium rather than just electronic switching. RAM’s are usually built from semi‐conductor integrated circuits, which can be dynamic (DRAM) or static (SRAM). Read Channel– Performs the data encoding and conversions the drive needs to write computer generated information onto a magnetic medium and then read that information with a high degree of accuracy. Read Verify‐ A data accuracy check performed by having the disk read data to the controller, which then checks for errors but does not pass the data on to the system. Read/Write Head‐ See Head. Recoverable Error‐ By ECC recovery or by re‐reading the data, a read error that the drive can correct Registry‐ See System Registry RLL (Run Length Limited) – An encoding scheme utilized during write operations to assist data read back.
ROM (Read Only Memory) – Integrated circuit memory chip containing programs and data that the computer or host cannot modify but only read.Instructions cannot be stored in ROM but the computer can only read instructions out of ROM. Rotational Latency‐ The amount of deferral in obtaining information from a disk due to the rotation of the disk.The average rotational latency for a disk is 5.8 which is rotating at 5200 RPM milliseconds. See also Mechanical Latency. RPM (Revolutions per Minute) –Spindle Speed is another name for the rotational speed of the media (disk). Hard drives typically spin at one constant speed. Mechanical latencies are higher the slower the RPM becomes. Disk RPM directly impacts the rotational latency which is why it is a critical component of hard disk drive performance. Dolphin Data Lab http://www.dolphindatalab.com/