Guide to DIGITAL OpenVMS Disk Services for Windows NT

1 Overview

This chapter contains the following sections:

• What is DIGITAL OpenVMS Disk Services for Windows NT?

• How is it Different from PATHWORKS?

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

• How Does it Work?

• What Hardware and Software Does it Require?

• Do I Need a License to Use it?

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

• Who Can Access its Disk Services?

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 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.

The following 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 respectively.

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 to back up both your Windows NT and OpenVMS data.

DIGITAL OpenVMS Disk Services for Windows NT also provides a flexible way of allocating storage. You can use it to divide large OpenVMS disks into smaller virtual disks and connect 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 Exchange mail server, and two 15 GB disks, one for your Lotus Notes server and one for your web server.

A fire destroys your Lotus Notes server. Its virtual disk is safe because it is being served by an OpenVMS Cluster that is distributed across various sites and survives the fire. 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.

1.2 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.

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

At any one time, only one Windows NT computer can connect to a particular disk service. That 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 this picture:

Figure 1-1 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.

The Windows NT computer at tier 2 uses TCP/IP to communicate with the OpenVMS Cluster at tier 1.

1.4 How Does it Work?

The following picture shows a single disk service. A container file on an OpenVMS disk stores the disk blocks for the virtual disk on the Windows NT computer.

The Windows NT computer is designed around the assumption that the probability of not being able to access any disk is low. This applies to virtual disks as well as to real ones. To fulfill the assumption, you must make sure that the disk service at the OpenVMS Cluster end is always available. You do this by setting up one or more standbys for each disk service that your OpenVMS Cluster provides, as described in Section 2.2.

In the previous picture, the active disk service is on GREEN, and there is a standby disk service on BLUE.

If GREEN fails, the service automatically fails over to BLUE. The failover is transparent to the Windows NT computer; users carry on using the service, unaware that it is now being provided by node BLUE.

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 3.4.

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.

1.5 What Hardware and Software Does it Require?

The following table shows the hardware and software you need to install Version 1.0 of DIGITAL OpenVMS Disk Services for Windows NT.

OpenVMS Alpha	Windows NT
An Alpha system that: Is running OpenVMS Alpha Version 7.1 Is running DIGITAL TCP/IP Services for OpenVMS Version 4.1 with the TIMA kit ECO#6 + installed Has at least 40,000 free blocks on its system disk	A Windows NT server or workstation (Intel or Alpha CPU) that: Is running Windows NT Version 4.0, with TCP/IP installed Has at least 8 MB of free disk space
+ This TIMA kit is included in the kit for Version 1.0 of DIGITAL OpenVMS Disk Services for Windows NT, and is placed in SYS$UPDATE when you install DIGITAL OpenVMS Disk Services for Windows NT.

1.6 Do I Need a License to Use it?

Yes, you need a license to use DIGITAL OpenVMS Disk Services for Windows NT. Your license controls how many different Windows NT computers can connect to the disk services on your OpenVMS Cluster at any one time.

Purchase the NTDS-DISK Product Authorization Key (PAK) and register it in your OpenVMS license database, as described in Installing DIGITAL OpenVMS Disk Services for Windows NT.

Note

Version 1.0 of the DIGITAL OpenVMS Disk Services for Windows NT software is certified for up to six concurrent connections to disk services on a single OpenVMS Cluster. For example:

• Six Windows NT computers can each connect to a different disk service on the OpenVMS Cluster, or

• One Windows NT computer can connect to six different disk services on the OpenVMS Cluster

1.7 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 cannot boot off it.

• Do not put paging files on it.

• Do not 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.

1.8 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, as described in Section 2.2.

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

  • If your routers are configured to allow messages to be broadcast to other subnets, the Windows NT administrator must know the subnet address of your OpenVMS Cluster.

  • Otherwise, the Windows NT administrator must know the IP address of the node in your OpenVMS Cluster that is currently providing the disk service.

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

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