Browse Prior Art Database

Remote Virtual Device Support

IP.com Disclosure Number: IPCOM000037016D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 69K

Publishing Venue

IBM

Related People

Blake, PR: AUTHOR [+2]

Abstract

This disclosure relates to the virtual machine (VM) operating system and remote virtual device support (RVDS). Both local and remote systems must be running VM. The concept disclosed enables VM users logged on to a local system access to virtual devices on a remote system. This is achieved by intercepting all I/Os to a virtual device and re-routing it to the remote system for execution. This is achieved by shipping the I/O request to a virtual machine on the local system, which sends the request via a communications link to a virtual machine on the remote system. Any device on any CPU can be used by any other CPU. RVDS consists of a set of modifications to VM/370 and a program that runs in a local and remote virtual machine connected together via a CTC.

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Remote Virtual Device Support

This disclosure relates to the virtual machine (VM) operating system and remote virtual device support (RVDS). Both local and remote systems must be running VM. The concept disclosed enables VM users logged on to a local system access to virtual devices on a remote system. This is achieved by intercepting all I/Os to a virtual device and re-routing it to the remote system for execution. This is achieved by shipping the I/O request to a virtual machine on the local system, which sends the request via a communications link to a virtual machine on the remote system. Any device on any CPU can be used by any other CPU. RVDS consists of a set of modifications to VM/370 and a program that runs in a local and remote virtual machine connected together via a CTC.

The remote devices currently supported are virtual minidisks. The minidisk is defined to the remote system in its VM directory and access is authorized on the local system. The user is unaware that the minidisk is on a remote system.

This allows user access to data across systems that do not need to be physically adjacent. Access is transparent to the user.

Briefly, user I/O for a remote minidisk is 'trapped' or intercepted by the local system control program; sent over a CTC link to the remote system associated with the real DASD; the remote system then executes the I/O operation and returns any data to the local machine and, hence, to the user. The advantage is that it allows one CPU to access data on a remote CPU without the use of shared DASD.

The RVDS program is illustrated in the Control Program (CP) and Disk I/O Dataflow which should be referred to in conjunction with the following brief description. In this description Surrogate is the name of the RVDS virtual machine on the local system and Mirror is the name of the RVDS virtual machine on the remote system. Remote Device is defined to CP. All I/O to the Remote Device is intercepted in CP.

CP communicates, via IUCV, to a Surrogate machine.

The Surrogate machine is coupled to a Mirror machine

via a CTC.

The CCWs (+ data) are sent to the Mirror.

The Mirror machine executes the CCWs and returns the

results

(+ data) back to the Surrogate machine.

The Surrogate machine passes this data back to CP

which, in turn,

passes it back to the User.

Any error conditions are reflected back...