Browse Prior Art Database

Skimming-less read preparation for space/locate command

IP.com Disclosure Number: IPCOM000011854D
Original Publication Date: 2003-Mar-20
Included in the Prior Art Database: 2003-Mar-20
Document File: 1 page(s) / 9K

Publishing Venue

IBM

Abstract

Disclosed is a mechanism for fast tape relocation on LTO tape drive by eliminating a backhitch.

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Skimming-less read preparation for space/locate command

   A dataset is a unit of write/read operation to/from a medium on LTO tape drive. Two numbers are assigned to a dataset to distinguish it from the other datasets. One is dataset number and the other is write pass number.

In order to start read operation from an arbitrary position on a medium, highest write pass number for 4 meter from 4 meter prior to the position needs to be searched first. Once highest write pass number is known prior to the position, a drive can start (normal) read operation using the write pass number as an initial number.

Since it takes time to switch from searching highest write pass number ("skimming" mode) to normal "read mode," there may be a chance to miss a right dataset just after the starting position and to read a wrong (old) dataset.

In order to avoid a chance to read a wrong dataset, "backhitch," a short length rewind, is used.

New method to avoid a chance to read a wrong dataset is to use "read mode" only, but with one more switch in a (hardware) data path. Read operation starts from 4 meter prior to the current position. The new switch is off for 4 meter to prohibit wrong data is sent to formatter. Once 4 meter is passed along, the switch becomes on to feed right data. Position sense for 4 meter may be synchronized with pattern detector in the input signal.

Pattern Detector

Decoder

Formatter

Digitized Data

Position Information

Disclosed by International Business Machines Corp...