Content Addressable File Store
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The Content Addressable File Store (CAFS) was a 1982 device developed by International Computers Ltd that provided a disk storage with built-in search capability. The motivation for the device was the discrepancy between the high speed at which a disk could deliver data, and the much lower speed at which a general-purpose processor could filter the data looking for records that matched a search condition.
Development of CAFS started in ICL's Research and Advanced Development Centre under Gordon Scarrott in the late 1960s. In its initial form, the search logic was built in to the disk head. A standalone CAFS device was installed with a few customers, including BT Directory Enquiries, during the 1970s.
The device was subsequently productised and incorporated as a standard feature within ICL's 2900 series and Series 39 mainframes. By this stage, to reduce costs and to take advantage of increased hardware speeds, the search logic was incorporated into the disk controller. A query expressed in a high-level query language could be compiled into a search specification that was then sent to the disk controller for execution. Initially this capability was integrated into ICL's own Querymaster query language, which worked in conjunction with the IDMS database; subsequently it was integrated into the VME port of the Ingres relational database.
ICL also produced a version of CAFS for its DRS minicomputer range called SCAFS (Son of CAFS). Unlike its mainframe cousin, this was implemented using custom firmware running on an industry-standard microprocessor. The device eventually became obsolete as memory prices dropped so only the largest databases cannot be kept in store. This removed any mass market for SCAFS and made it uneconomic.
