Browse Prior Art Database

Error Recovery Procedure

IP.com Disclosure Number: IPCOM000100379D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Lane, KW: AUTHOR [+3]

Abstract

A multi-path storage system control unit contains more than one storage path with a channel switch and device connector bus attached to each storage path. At any point in time, each storage path can communicate with one channel through the channel switch and one device through the device connection bus. The storage paths share a common memory to communicate with each other and a common cache memory to store and buffer data.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Error Recovery Procedure

       A multi-path storage system control unit contains more
than one storage path with a channel switch and device connector bus
attached to each storage path.  At any point in time, each storage
path can communicate with one channel through the channel switch and
one device through the device connection bus.  The storage paths
share a common memory to communicate with each other and a common
cache memory to store and buffer data.

      A storage path can improve subsystem performance by moving data
within the subsystem so that it is available with minimum delay when
required.  An internal command chain is executed to move the data
between the disk devices and the cache memory.  When a subsystem
error occurs during the internal command chain process, the storage
path will retry the same channel command word for failures due to a
data check or an overrun error.  For failures due to an equipment
check error within the storage path itself, the storage path will
restart the internal command chain for a limited number of retries.
If the error persists, the storage path will exhaust the retry count
and abort the command chain.  The internal command chain is retried
on another available storage path.  The control unit thereby is
capable of communicating with the same device by executing any
command chain on any available storage path.

      If permanent failures are encountered on the executing storage
path and the retry count is ex...