3.3. Network-Attached Storage
Like the acronym SAN, NAS is largely a marketing term that has, through repeated use, gained a technical definition. The primary distinction between NAS and SAN rests on the difference between data files and data blocks. NAS transports files; SANs transport blocks. NAS uses file-oriented delivery protocols such as NFS and CIFS, whereas SANs use block-oriented delivery protocols such as SCSI-3. Because data blocks are the raw material from which files are formed, NAS also has a block component. These blocks are addressed on a per-file basis, using meta-data (directory information) to determine which file to use. The block access methods of a NAS device, however, are typically hidden in the NAS enclosure. To the outside ...
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