A Winchester disk also consists of multiple (two or more)hard disk platters mounted on a single central shaft. However, the main difference between a Winchester disk and a disk pack is that Winchester disks are of fixed type. That is, the hard disk platters and the disk drive are sealed together in a contamination free container and cannot be separated from each other. Hence as opposed to disk packs, which have virtually unlimited capacity, Winchester disks have limited capacity. However, for the same number of disk platter of the same size, Winchester disks can manage to have larger storage capacity than disk packs due to the following reasons.
Because both the disk platters and the disk drive are sealed in a contamination free container and do not require to be separated later, all the surfaces of all the disk platter(including the upper surface of the topmost platter and the lower surface of the bottommost platter) are used for data recording in case of Winchester disks. That is for a Winchester disk with four platters, there are eight surfaces on which data can be recorded as opposed to six surfaces in case of a disk pack with four platters.
The contamination-free environment allows Winchester disks to employ much greater precision of data recording and accessing resulting in greater density of data storage than the interchangeable disk packs.
The storage capacity of today Winchester disks is usually of the order of a few tens of megabytes to a few gigabytes (10 bytes).
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