Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Packet Send-Ahead for Magneto-Optic Library

IP.com Disclosure Number: IPCOM000099849D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Willson, DL: AUTHOR [+2]

Abstract

Optical disk drives may not read or write at sufficiently high datarates to allow direct channel attach to the host. When this occurs, files can be segmented into discrete packets of a finite size and data is transferred by the reading or writing of a series of these discrete packets. A diagram of a host, control unit, and optical drive is shown in the figure.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Packet Send-Ahead for Magneto-Optic Library

       Optical disk drives may not read or write at sufficiently
high datarates to allow direct channel attach to the host. When this
occurs, files can be segmented into discrete packets of a finite size
and data is transferred by the reading or writing of a series of
these discrete packets.  A diagram of a host, control unit, and
optical drive is shown in the figure.

      When an optical drive finishes writing and, if necessary,
verifying a packet, then the drive spins while waiting for the next
packet.  If the path length in time from the host (10) through the
control unit (20) to the drive (30) is shorter than the time for the
optical disk to complete one spin, then the spin time of the disk is
the critical path.  Thus, when the optical drive is spinning the
optical disk at low RPM (revolutions per minute), packets may be kept
at the host level without a loss in write EDR (effective data rate).

      This disclosure is concerned with drives which spin the optical
disk at a high RPM.  If packets to be written were kept at the host
level, then the more rapidly spinning disk could lose several
revolutions while waiting for the next packet.  Under these
circumstances, the write EDR would be less than optimal.

      To enhance the EDR of optical drives which write packetized
data, the following solution is proposed. Packets are sent ahead by
the host and kept at the control unit level until needed by the
optical drive.  For data reliability reasons, the packet being
written by the drive can be held by the control unit until that
packet has been verified....