FR2160384B1 - - Google Patents

Abstract

1378983 Digital data storage INTERNATIONAL BUSINESS MACHINES CORP 6 Oct 1972 [17 Nov 1971] 46161/72 Heading G4C Data are written on sequential tracks of a disc stack cylinder until a break point is reached, after which data are written on another disc stack or on sequential tracks of another cylinder of the same stack. In one embodiment having three disc packs each with 20 disc faces, each block of data in a string corresponds in length to one track on a disc. Assuming module 0 has a first available track at cylinder 2, face 5, the first 15 blocks of a string are recorded on faces 5-19 of cylinder 2 and the next 5 blocks of the string are recorded on cylinder 3 starting at face 0, for example. Blocks 20 are recorded in module 1, for example at first available cylinder 5 of faces 10-19 and cylinder 6 of faces 0-9. Similarly blocks 40-59 are recorded in module 2 at first available cylinder 1 of faces 4-19 and cylinder 2 of faces 0-3. This arrangement may require head movement for each group-of 20 blocks, depending on the location of the first available face in each module. In a second embodiment, blocks are recorded in succession on the first available faces in each module taken in turn and head movement only takes place if overflow from the last module occurs. Taking the same example as above, blocks 0-14 are recorded in module 0, cylinder 2, faces 5-19; blocks 15-24 in module 1, cylinder 5, faces 10-19; blocks 25-39 in module 2, cylinder 1, faces 4-18; block 40 in module 2, cylinder 1, face 19; blocks 41-59 would then be recorded in module 0, cylinder 3, faces 0-18. Algorithms for calculating the addresses of the various blocks in storage are described.