Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Patent
1990-04-19
1991-09-17
Psitos, Aristotelis
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
360 32, 360 53, 360 744, G11B 5588, G11B 509, G11B 1520
Patent
active
050500180
ABSTRACT:
A helical drive system (10) reads tracks (18) on a storage medium (12), including tracks which appear as distorted tracks. Each track (18) comprises a plurality of blocks of data, with each block having unique block-identifying information. A track-following servo system (84) causes a read head (16C) to traverse predetermined original azimuthal paths (P0) across the storage medium (12) for reading the blocks recorded along each of the original azimuthal paths (P0). A controller (50) uses the block-identifying information to determine whether any blocks expected to be read during the traversal of the original azimuthal paths (P0) were not read. If expected blocks were not read, the controller (50) repositions the storage medium (12) and directs that the medium (12) be re-read with the head (16C) positionally offset until the expected blocks are actually read. During the re-read attempts, the read head (16C) is positionally offset to traverse sets of modified azimuthal paths (P1, P2, P3, . . . P10 ). Each set of modified azimuthal paths (P2, P3, . . . P10) is offset with respect to the original azimuthal paths (P0) relative to a direction of medium travel (15), thereby providing opportunities to read blocks which would not otherwise be read due to distortion of the tracks (18). In one mode of the invention, the controller (50) dynamically selects from among a plurality of offset degree values based on the historical success rate of the differing offsets in reading blocks which formerly were missing blocks.
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Georgis Steven P.
Pisciotta E. Christopher
Exabyte Corporation
Garland Steven R.
Psitos Aristotelis
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