C ‐ Data Recovery Glossary Cable Select (CSEL) ‐ An alternative option which can be used in place of setting Master/Slave jumpers in the designation of drives in a dual drive configuration. Master/Slave designation is based on the position of drives relative to the cable. Special cabling is required by the system manufacturer to selectively ground the CSEL signal on one of the IDE cable connectors. For example, when one of the drives is connected to the grounded CSEL conductor, it configures itself as a Master. When the second drive is connected to the other connector, on which CSEL is not grounded, it becomes slave. This eliminates the need for unique jump ring configuration between the Masters and slave drives. Cache‐ High‐speed RAM is used as a buffer between the CPU and a hard drive. The cache retains recently accessed information to speed up subsequent access to the same data. When data is read from or written to disk, a copy is saved in a cache, along with the associated disk address. The cache monitors the addresses of subsequent read operations to see if the required data is already in the cache. If it is, the drive returns the data immediately. If it is not in the cache, than it is fetched from the disk and saved in the cache. Capacity‐ The amount of information, measured in bytes that can be stored on a hard drive. It is also known as “Storage Capacity”. Card‐ A circuit board that is usually designed to plug into a connector or slot. See also adapter. CAR‐ An acronym for re writable CD’s technology by which media can be written to and erased approximately 1,000 times before failure. Standard 74 min CD‐RW media can hold up to 500 MB when formatted for fixed length packet writing. Channel‐ A connection or socket on the motherboard or controller card. A mother board may have one or two channels (primary and Secondary). If your motherboard has only one channel, you may need to add a controller card to create a secondary channel . Channel Assembly – In the computer industry, the final assembly of a system by a distributor or reseller from kits, provided by the manufacturer and from components shipped directly to the assembler by subsystem makers. Clean Room – An environmentally controlled dust‐free assembly or repair facility in which hard disk drives are assembled or can be opened for internal servicing. See our Clean Room Components .
Click – To click an item means to point to it with the screen pointer, and then press quickly and release the left mouse button at once. Cluster – Windows allocate space to files in units called Clusters. Each cluster contains from 1 to 64 sectors, depending on the type and size of the Disk. A cluster is the smallest unit of Disk space that can be allocated for the usage by the files. A hard disk term refers to a group of sectors, the smallest storage unit recognized by the DOS. On the most modern hard disk, 512‐byte sectors make up a cluster, and one or more clusters make up a track. CMOS – A part of the motherboard that maintains a system variable in static RAM. It also supplies a real‐time clock that keeps track of the date, day and time. CMOS Setup is typically accessible by entering a specific sequence of keystrokes during the POST at system start‐up. Cold Bolt – Starting or restarting a computer by turning On the power supply. See also Warm Boot. Command Aging – An SCSI feature that prevents the command of reordering algorithm from keeping I/O process on waiting in the command queue for the extended period of time. Command Queuing – A feature that enables the drive to receive I/O processes from one or more initiators and execute them in an optimum sequence. Command Reordering ‐ A feature that allows the drive to reorder I/O processes in the command queue, which results in minimizing the seek time and rotational latency and thus increases throughput. Context Menu – Also called a context‐sensitive menu, or a shortcut menu, a context menu includes the commands which are commonly associated with an object on the screen. To activate an items context menu, point to it with the screen pointer, then press and release the right mouse button once. Controller – See disk controller, interface controller, and disk drive controller. Controller Card – An adapter with an electronic control for one or more hard drives. Usually install in a bus slot in the computer. Cookies – (Internet Browser) – Holds information on the times and dates you have visited web sites. Other information can also be saved to your hard disk in these text files, including information about online purchases, validation information about you for members‐only web sites, and more.
Correctable Error – An error the drive can correct by using Error Detection and Correction schemes. CPU – Stands for Central Processing Unit, a programmable logic device that performs all the instruction, logic, and mathematical processing in a computer. Crash – A sudden, usually drastic failure. It can be said of the operating system or a particular program when there is a software failure. Also, a disk drive can crash because of hardware failure. CRC – Acronym for Cyclic Redundancy Check. The CRC is used to verify data block integrity. In a typical scheme, 2 CRC bytes are added to each user data block. The 2 bytes are computed from the user data, by digital logical chips. The mathematical model is made up of polynomials with binary coefficients. When reading back data, the CRC bytes are read and compared to new CRC bytes computed from the read back block to detect a read error. The read back error check process is mathematically equivalent to dividing the read block, including its CRC, by a binomial. If the division remainder is zero, the data is error free. Cross‐linked files – Two files, both refer to the same data. Cylinder – The cylindrical surface formed by identical track numbers on vertically stacked discs. At any location of the head positioning arm, all tracks under all heads are the cylinder. The cylinder number is one of the three address components required to find a specific address. The other two are head number and sector number. Cylinder, Head, Sector (CHS) Addressing – A method of referencing the sectors on a drive, as a collection of unique cylinders, head and sector addresses. Each block on the drive will have a unique cylinder, head and sector address. Dolphin Data Lab http://www.dolphindatalab.com/