1 Overview

This chapter introduces DIGITAL OpenVMS Disk Services for Windows NT:

• What is DIGITAL OpenVMS Disk Services for Windows NT?

• What Benefits Does it Give Me?

• How is it Different from PATHWORKS?

• How Does it Fit into the 3-Tier Client- Server Environment?

• How Does it Work?

• What Can't I Do With its Virtual Disks?

• Who Can Access its Disk Services?

• Where Can I Get the Latest Information?

1.1 What is DIGITAL OpenVMS Disk Services for Windows NT?

DIGITAL OpenVMS Disk Services for Windows NT lets you use your OpenVMS Cluster to store Windows NT data. The OpenVMS Alpha nodes in your cluster serve virtual disks to Windows NT computers.

On the Windows NT computer, you format the virtual disk with a native Windows NT file system, such as NTFS. It behaves just like a locally attached disk, although its data is actually stored in a container file on your OpenVMS Cluster.

This picture shows a Windows NT computer whose D: and E: drives are virtual disks whose data is stored in the OpenVMS container files MOVIES.NTDS and SPORTS.NTDS.

1.2 What Benefits Does it Give Me?

DIGITAL OpenVMS Disk Services for Windows NT gives you centralized storage. You can store Windows NT data on your OpenVMS Cluster, and you can use your existing OpenVMS backup schedules and tools to back up both your Windows NT and OpenVMS data.

It also provides a flexible way of allocating storage. You can use it to divide large OpenVMS disks into smaller virtual disks and serve each virtual disk to a different Windows NT computer.

For example, your OpenVMS Cluster has a 60 GB RAID array that you want to use to provide storage for three Windows NT application servers. You create three virtual disks:

• A 30 GB disk for your Microsoft Internet Information server

• A 15 GB disk for your Lotus Notes server

• A 15 GB disk for your Microsoft SQL server

A fire destroys your Lotus Notes server, but does not affect your OpenVMS Cluster. So to get the notes service up and running again, you simply use DIGITAL OpenVMS Disk Services for Windows NT's point-and-click interface to connect another Lotus Notes server to the virtual disk.

Note that DIGITAL OpenVMS Disk Services for Windows NT does not run on OpenVMS VAX. In a mixed architecture OpenVMS Cluster, only the OpenVMS Alpha nodes can provide disk services.

1.3 How is it Different from PATHWORKS?

PATHWORKS and DIGITAL OpenVMS Disk Services for Windows NT provide Windows NT computers with very different types of services:

• PATHWORKS provides file services and print services.

  The file services let you share data between OpenVMS and Windows NT applications. Both OpenVMS and Windows NT applications can access the same files.

• DIGITAL OpenVMS Disk Services for Windows NT provides disk services.

  It serves raw disk blocks, not files, to the Windows NT computer that is connected to the service. OpenVMS applications cannot access the data stored on the virtual disk, just as they cannot access the data stored on a real disk that is locally attached to the Windows NT computer.

DIGITAL OpenVMS Disk Services for Windows NT is for customers who want to store Windows NT data on OpenVMS Clusters, but who do not need to share files between OpenVMS and Windows NT applications. If you need to share data between OpenVMS and Windows NT applications, you must use a file sharing solution such as PATHWORKS.

1.4 How Does it Fit into the 3-Tier Client-Server Environment?

The Windows NT computer can share the virtual disk out to other computers, in the same way that it can share its real disks out to other computers. This makes DIGITAL OpenVMS Disk Services for Windows NT the ideal fit for the 3- tier client-server environment shown in the following picture.

Figure 1-1 The 3-Tier Client-Server Environment

The OpenVMS Cluster at tier 1 serves disk storage to Windows NT servers at tier 2, which share it out to user workstations at tier 3.

Note that with PATHWORKS, you cannot share data with a third tier in this way. PATHWORKS is designed for the 2-tier environment where the OpenVMS Cluster serves files, via PATHWORKS shares, direct to user workstations.

1.5 How Does it Work?

This picture shows a Windows NT computer that is connected to a single disk service.

A container file on an OpenVMS disk stores the disk blocks for the virtual disk, drive E:, on the Windows NT computer. Drive E: looks like a local disk and is formatted with a native Windows NT file system, such as NTFS.

In the OpenVMS Cluster, node GREEN is currently providing the service, and node BLUE is configured as a standby. If GREEN fails, the service automatically fails over to BLUE. The failover is transparent to the Windows NT computer; users carry on accessing drive E: without any interruption.

The Windows NT computer uses TCP/IP to communicate with the OpenVMS Cluster and to transfer data to and from the container file.

Tips

For optimum availability, configure two or more network interconnects between the Windows NT computer and the OpenVMS Cluster.

For example, if you have two FDDI connections between the Windows NT computer and the cluster, if one of the FDDI links fails the other one automatically takes over, transparently to users.

Only one Windows NT computer can connect to a particular disk service at any one time.

If the computer currently connected to the service fails, you can connect a different Windows NT computer to the service, as described in Section 3.5.

Caution

You can corrupt your data if you connect a different Windows NT computer to the service and the original Windows NT computer restarts.

When the original Windows NT computer restarts, it automatically tries to reconnect to the service. If the service happens to fail over from one node in the OpenVMS Cluster to another while it is restarting, it might succeed in reconnecting to the service, stealing the connection back from the other Windows NT computer. If this happens, your data could be corrupted.

To avoid data corruption, never connect another Windows NT computer to a disk service if there is any possibility that the original Windows NT computer could reconnect to it.

For example, it is safe to connect another computer to the service if the original computer was destroyed in a fire, or if you have removed its network cards so that when it restarts it will not be able to communicate with the OpenVMS Cluster that is providing the service.

1.6 What Can't I Do With its Virtual Disks?

You can use a virtual disk created by DIGITAL OpenVMS Disk Services for Windows NT just like a real disk that is locally attached to the Windows NT computer, with the following restrictions:

• You can't boot off it.

• Don't put paging files on it.

• Don't create a volume set, a mirror set, or a stripe set on it.

  If you want striping or mirroring, create the container file on an OpenVMS disk that is striped or shadowed.

1.7 Who Can Access its Disk Services?

A Windows NT computer can connect to a disk service on your OpenVMS Cluster provided that:

• Another Windows NT computer is not currently connected to the disk service. Only one Windows NT computer can connect to a given disk service at any one time.

• The administrator of the Windows NT computer knows the names that you chose to identify both the disk service and your OpenVMS Cluster (see Section 2.2).

• If the Windows NT computer is in a different subnet from your OpenVMS Cluster, the Windows NT administrator knows either:

  • The subnet address of your OpenVMS Cluster (if your routers are configured to allow messages to be broadcast to other subnets)

  • The IP address of the node that is currently providing the disk service (if your routers are not configured to allow messages to be broadcast to other subnets)

• You registered the name of the Windows NT computer in your license database, using the LICENSE command with the /RESERVE qualifier.

1.8 Where Can I Get the Latest Information?

For the latest information on DIGITAL OpenVMS Disk Services for Windows NT, including product updates and documentation, visit our web site at:

http://www.openvms.digital.com/openvms/products/ntds/

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