Storage block

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A storage block is a physical sector on the surface of a disk or diskette. It is the smallest unit of transference between the main memory and a given disk drive.

In the IBM mainframe terminology, a block is the minimal physical division of data in a disk drive, either as used on a Fixed Block Architecture (FBA) disk or in the Cylinder-Head-Record (CCHHRR) addressing mode of a Count-Key-Data (CKD) disk.^{[citation needed]} Blocks are separated on the track by "inter-record gaps" (approx. 6 bytes on IBM 3380 and IBM 3390 disk drive models). The number of blocks per tracks depends on the block size and the specific gap size associated to each block. Each block can contain a discrete quantity of logical records or it can be empty. Logical records are defined by the database designer or application designer; see Data set (IBM mainframe).