Browse Prior Art Database

Prefix Staging Technique for Optical Libraries in Network Environments

IP.com Disclosure Number: IPCOM000118157D
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Dewey, DW: AUTHOR

Abstract

In order to smooth out delays when accessing an optical library in a Local Area Network (LAN) environment, a prefix of the data of a file is cached on the library controller hard disk so that the library may begin responding to data read requests while the disk with the remainder of the file is being physically mounted in a drive.

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

Prefix Staging Technique for Optical Libraries in Network Environments

      In order to smooth out delays when accessing an optical library
in a Local Area Network (LAN) environment, a prefix of the data of a
file is cached on the library controller hard disk so that the
library may begin responding to data read requests while the disk
with the remainder of the file is being physically mounted in a
drive.

      Optical libraries in LAN environments provide cost effective
near on-line storage that appears as a standard single device and
file system.  The one negative of the optical library is that the
first access to a set of files may have a delay of up to 15 seconds
while a cartridge is being mounted.  In LAN environments where the
library is transparent, the system displays no messages or special
communications to the end user.  This presents two problem scenarios:
  o  LAN timeout values in the rest of the system may not be
      high enough since they are designed for on-line devices.
  o  The user perceives the delay as a hang and cancels the
      operation.

In small LANs, these problems have been addressed by having the users
of an optical library increase the requestor timeout values.
Likewise, all users on the LAN are aware of the optical library and
expect the occasional delay.  Neither of these solutions scale well
to larger networks.  This disclosure presents a technique that could
be incorporated into an optical library serving as a file server that
would alleviate these two scenarios.

      The proposed solution is to have the library controller store
on DASD a prefix of the data of the file.  An example size would be...