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No Guard Wrap Partitioning

IP.com Disclosure Number: IPCOM000241453D
Publication Date: 2015-Apr-30

Publishing Venue

The IP.com Prior Art Database

Abstract

Legacy partitioning of tape drive waisted capacity of guard wraps. This invention increase the tape volume capacity by eliminating the guard wraps by shifting the reader head position.

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This is the abbreviated version, containing approximately 33% of the total text.

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No Guard Wrap Partitioning

Legacy partitioning of tape drive waisted capacity of guard wraps.

This invention increase the tape volume capacity by eliminating the guard wraps by shifting the reader head position.

Problems that needs to be solved


Use of partition on tape drives
Linear Tape Open (LTO) tape drive generation 5 or later, and Enterprise Tape Drive TS1140 or later support a mechanism of partition which divides a tape volume logically into multiple partitions. The partition ideally aims to improve of effective data management and to realize high speed data access but is mainly provided to support Linear Tape File System (LTFS). There is no tape drive users who utilize the partition mechanism other than LTFS.

LTFS realize the file system by dividing a tape volume into two separate partitions called a data partition where the data of the file is stored in the data partition and an index partition which records the attribute of the file (file name, file size, physical position of the file data on the tape, access control list, etc) corresponding to the files in the data partitions. The LTFS reports the file system information to the operating system so that the operating system user can recognize files on the file system on one physical volume.

Creation of partitions on tape medium


Tape drive has writer heads with multiple tracks to write multiple number of data bits on the tape simultaneously. Recent tape drive supports 32 data tracks and has capability to write 32 bits of data simultaneously.

Four data bands are defined on the tape and each band is sectioned in multiple number of regions called wraps. The latest tape drive has 20 wraps in each data band. Each wrap is defined from multiple number of tracks. The latest model has 32 tracks. Therefore 4 [data bands] x 20 [wraps/data band] x 32 [tracks/wrap] = 2,560 tracks are defined on a tape.

In order to record more data on a tape medium, the newer the tape drive generation, the narrower the track pitch of writer head. On the other hand the data on tape medium which was written by the drive of former generation must be read back by the newer generation drives.

To support compatibility between generations, the track pitch of the writer head corresponds to the widest pitch which is supported by the tape drive, whereas the reader head track pitch corresponds to the narrowest width. A part of the data on the tape written by the writer head is overwritten by the data written on the next data track.

For example, the track pitch of LTO5 is defined to 8.10 um and the one of LTO6 is define narrower to 4.75 um. The LTO6 drive writes 8.10 um width of data using the writer head on a certain wrap. On the next wrap the writer head shifts 4.75 um from the previous wrap position so that the remaing 8.10 um - 4.75 um =
3.35 um region is to be overwritten.

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The tape drive is so called a sequential access device and the data is written from top to bottom sequentially. Without pa...