Browse Prior Art Database

Fast-Read Optical Disk Drive

IP.com Disclosure Number: IPCOM000110809D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Dimitri, KE: AUTHOR [+3]

Abstract

Currently, optical disk drives are designed to read and write at the same device channel speed. However, an analysis of customer workloads indicates that the writing of data to optical tends to take place during a batch window comprising the second and third work shifts. This batch write process is essentially the staging of data which had been on magnetic DASD to the next lower level in the data storage hierarchy, optical. Since the actual write data rate of the optical devices is gated only by the length of the batch window, which is several hours long, the write effective data rate is really judged by a binary, go/no-go criterion.

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Fast-Read Optical Disk Drive

      Currently, optical disk drives are designed to read and write
at the same device channel speed.  However, an analysis of customer
workloads indicates that the writing of data to optical tends to take
place during a batch window comprising the second and third work
shifts.  This batch write process is essentially the staging of data
which had been on magnetic DASD to the next lower level in the data
storage hierarchy, optical.  Since the actual write data rate of the
optical devices is gated only by the length of the batch window,
which is several hours long, the write effective data rate is really
judged by a binary, go/no-go criterion.

      The primary workload during the first shift is the reading of
data from optical.  The personnel at the workstations desire the
files, image objects, records, etc., quickly, as time is money.
Every second matters.  Customers measure their read response times
very carefully, especially when files are retrieved from optical in
response to telephone inquiries.  Thus, the read data rate of the
devices is the critical path in the acceptance of optical devices.

      Our solution is to spin the optical media at two different
speeds; one for reading and one for writing.  The write speed is
dictated in part by laser power, as the laser power must increase by
the square root of the angular velocity of the media.

      However, the read operation takes far less power than write
operations.  Even though the square-root law still applies to the
read laser power, the tiny read...