Browse Prior Art Database

Cache Port Fencing for Dual Cache Subsystem

IP.com Disclosure Number: IPCOM000118534D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Bearsdley, BC: AUTHOR [+4]

Abstract

In a continuously-available DASD control unit that contains two cache storages and two nonvolatile storages, minimizing the subsystem performance impact of hardware logic failures has great importance.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Cache Port Fencing for Dual Cache Subsystem

      In a continuously-available DASD control unit that contains two
cache storages and two nonvolatile storages, minimizing the subsystem
performance impact of hardware logic failures has great importance.

      This disclosure identifies a method to determine the correct
resource from service when a permanent hardware failure is detected
in the path between a storage path and a cache or nonvolatile
storage.

      In a dual-cache subsystem with two storage directors that each
contain two storage paths, the decision to fence (remove from
service) a storage path, cache storage, or nonvolatile storage
resource is determined by the following subsystem conditions:
  o  Both cache storages and both nonvolatile storages are
      available:
     The Figure shows the data and control paths that interconnect
      the storage paths and storage resources.
     - If no storage path-to-device fence, DASD controller fence,
        or storage path fence has been applied against the other
        storage path in the storage director that contains the
        storage path that encountered the failure and neither
        storage path in the second storage director is fenced,
        the following occurs:
       1.  The storage path that detects the failure will fence
            itself and report the failure to the support facility.
       2.  The support facility will determine if the failure is
            more likely a storage path error, a cache storage
            error and perform one of the following actions:
           - If the error is more likely to be cache storage
              error, the support facility will request that the
              cache storage associated with the failure be
              fenced.  After the cache storage is fenced, the
              fenced storage...