Browse Prior Art Database

Device Addressing with Variable Drawer Configurations

IP.com Disclosure Number: IPCOM000115768D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Hren, A: AUTHOR [+10]

Abstract

A method for changing the number of logical volumes in a drawer in a rack without disrupting access to the other logical volumes in the rack is disclosed. Channel Connection Addresses (Logical Volume addresses as known by CPUs) freed by removing the old drawer are reused and, if the new drawer has more logical volumes than the old drawer, the next unused Channel Connection Addresses are used.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Device Addressing with Variable Drawer Configurations

      A method for changing the number of logical volumes in a drawer
in a rack without disrupting access to the other logical volumes in
the rack is disclosed.  Channel Connection Addresses (Logical Volume
addresses as known by CPUs) freed by removing the old drawer are
reused and, if the new drawer has more logical volumes than the old
drawer, the next unused Channel Connection Addresses are used.

      In a subsystem with a control unit providing a RAID function,
the logical volumes are spread across multiple physical devices.

      The control unit will maintain Global Subsystem Status on a
reserved track on two of the logical volumes.  The Rack, the Control
Unit and the attaching CPUs may address each Logical Volume
differently.  The Global Status contains these three different
addresses for each Logical Volume in the Subsystem.

      Each Logical Volume Address for the Rack is fixed by the Drawer
location and the logical sequence of the volumes within the Drawer.
As Drawers are installed, the control unit will sequentially assign
the Logical Volume Addresses for the Control Unit and the Channel
Connection Addresses for the CPUs.
  Table 1. Table 1 Device Addressing with Variable Drawer
Configuration
  Drawer Number               Addressing
  00            CPU           00            01         --         --
                Control Unit  00            01         --         --
                Rack          20            21         --         --
  01            CPU           02            03         --         --
                Control Unit  02            03         --         --
                Rack          24            25         --         --
  02            CPU           04            05         --         --
                Control Unit  04            05         --         --
                Rack          28            29         --         --
  03            CPU           06            07         --         --
                Control       06            07         --         --
                Rack          2C            2D         --         --

      Table 1 defines the Logical Volumes Addresses for a Rack that
contains four Drawers with two Logical Vol...