<Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (May 2013) (Learn how and when to remove this template message) </Td> </Tr> <Ol> <Li> Track </Li> <Li> Geometrical sector </Li> <Li> Track sector </Li> <Li> Cluster </Li> </Ol> <P> In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc . Each sector stores a fixed amount of user - accessible data, traditionally 512 bytes for hard disk drives (HDDs) and 2048 bytes for CD - ROMs and DVD - ROMs . Newer HDDs use 4096 - byte (4 KiB) sectors, which are known as the Advanced Format (AF). </P> <P> The sector is the minimum storage unit of a hard drive . Most disk partitioning schemes are designed to have files occupy an integral number of sectors regardless of the file's actual size . Files that do not fill a whole sector will have the remainder of their last sector filled with zeroes . In practice, operating systems typically operate on blocks of data, which may span multiple sectors . </P>

Sectors are typically how many bytes in size
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