Browse Prior Art Database

Segmented Paging With Immediate Data Availability

IP.com Disclosure Number: IPCOM000087490D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Bresemann, DH: AUTHOR [+4]

Abstract

A mass storage system (MSS) simultaneously services a plurality of independent central processing unit (CPU) hosts. MSS consists of a mass storage control (MSC) controlling a staging storage facility (SSF) which is independently accessible by the respective CPU host via an I/O connection using a virtual address space. Each CPU host has its own independent virtual address space. Typically, SSF consists of a plurality of direct access storage device (DASD) units wherein virtual volumes (VV) are virtually mounted upon virtual spindles (VUA).

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Segmented Paging With Immediate Data Availability

A mass storage system (MSS) simultaneously services a plurality of independent central processing unit (CPU) hosts. MSS consists of a mass storage control (MSC) controlling a staging storage facility (SSF) which is independently accessible by the respective CPU host via an I/O connection using a virtual address space. Each CPU host has its own independent virtual address space. Typically, SSF consists of a plurality of direct access storage device (DASD) units wherein virtual volumes (VV) are virtually mounted upon virtual spindles (VUA).

The virtual spindles are an address space logically assignable by MSC for each job wherein a VV is virtually mounted on a VUA. Accordingly, in SSF each VV is spread over a plurality of independent real units. For minimizing addressing and increasing data availability, each VV is divided into a plurality of "pages". Typically, each VV has 50 pages of data, each consisting of a plurality of DASD cylinders.

Data is made available to the CPU host through SSF by staging and destaging data signals from and to a mass storage facility (MSF) which may be an automatic tape storage unit. Staging and destaging under control of MSC contains a plurality of independent data paths and can operate independently of the 1/0 transfers. Generally, when a CPU host asks MSC for a particular VV, only a portion of the VV is actually staged from MSF to SSF and then according to a predistribution concept. That is, the VV is spread over a plurality of real DASD units for increasing data availability.

The request for allocating space by a CPU host to MSC constitutes a request for staging data from MSF to SSF. Such request may include a plurality of such pages of each VV. Since each such request contains a relatively large number of data signals, the staging operation can extend over a long period of time, such as several minutes. As such, the data signals first st...