Migration to Windows NT Server

Clevin Wong

Introduction

In order to provide better computing performance, the Computing Services Centre (CSC) has undergone a series of changes in adopting the departmental server software platform. The changes can be summarized in the table :

Generation	Client Software	Server Software	Departmental Server Machine Type
1	Pathworks Client for DOS V2 to V4	Pathworks Server for VMS V2 to V4	MicroVAX 2000
2			VAXstation / VAXserver 3100
3			VAXstation 4090
4	Pathworks Client for DOS V5	Windows NT Server V3.51	Pentium PC

Table 1. Brief History of our Departmental Network Server

For the first three generations of the departmental network server, the software Pathworks Server for VMS running on a Digital VAX machine was used. After the upgrade of the client software to Pathworks Version 5, the departmental servers have been switched to a different platform with Pentium PC running Windows NT Server software. In this article, we will briefly discuss the reasons behind the selection of the server software platform.

Selection of Candidates

Although the major client software is Pathworks Client for DOS V5, it does not mean that Pathworks Server for OpenVMS V5 is the only candidate for the server software. Since the Pathworks Client software is fully compatible with the ¹LAN Manager V2 Client software , we can also consider other server software which is compatible with the LAN Manager V2 Server. However, the new client software must offer a seamless integration with the existing network and host services. In this respect, two candidates are chosen for our environment. They are :

Pathworks Server for OpenVMS V5 (latest version V5.0c) running on a DEC Alpha 2000 machine.
Windows NT Server V3.51 running on a Pentium PC and/or DEC Alpha machine or other platforms.

As its name implies, the "Pathworks Server for OpenVMS V5" runs on the platform of a Digital VAX or Alpha machine with the OpenVMS operating system. The software can function as a LAN Manager V2.2 server, with some add-on services like ²DECnet and ³LAT support.

On the other hand, Windows NT Server (previously known as "Windows NT Advanced Server") functionally is the latest enhanced version of the LAN Manager. It can provide a superset of services offered by a LAN Manager V2 Server. For this reason, it has the nicknames "LAN Manager V3.0" and "LAN Manager for NT".

Findings

a. Pathworks Server for OpenVMS V5

The Pathworks Server has the advantages that it provides the support for DECnet and LAT. However, during the test runs, some drawbacks were experienced. Firstly, the software is still not very mature. Abnormal crashes of the server processes were sometimes encountered. Some network protocols do not work as expected, and there are still some unsolved problems. Secondly, although the Alpha machine is a very powerful and efficient computer (as shown in the performance increase in our new CityU Polylink server), the performance of the Pathworks Server on this machine is below our expectation. One of the reasons leading to the degrade of performance is that OpenVMS uses complex RMS (Record Management System) for the file systems which mismatches with the simple file organization in MS-DOS. Moreover, the "License Requester" mechanism of Pathworks is very hard to manage. Additional licenses for non-Pathworks clients such as Windows NT and Windows 95 have to be purchased.

b. Windows NT Server V3.51

As mentioned before, Windows NT Server maintains compatibility with the LAN Manager V2 Server while at the same time, offers extended features and services. There are many useful enhancements, including :

It simplifies the ⁴domain management by decreasing the server types from four (primary domain controller, backup controller, member servers and standalone servers) to three (primary domain controller, backup controllers and servers);
Instead of requiring an account for each domain, a user can have a single network-wide login;
It supports the "trusted domains" relationship that allows pass-through authentication among domains. A domain can be set to "trust" the users of another domain, thus providing a mechanism for account management that spans many domains and potentially, many subnets.
It can support unlimited number of ⁵groups.
It supports ⁶local groups.

Conclusion

In the test runs, it was found that the NT Server is more stable than the Pathworks Server with a significant performance increase. With respect to the licensing and connectivity with non-Pathworks Clients like the popular Windows 95 and Windows NT clients, the NT Server provides a direct and simple mechanism to serve them without additional license fee. Unlike the Pathworks Server for OpenVMS which is a machine dependent software, Windows NT Server can run on many different platforms, including the Alpha machine. Hence, it can be easily switched from a Pentium PC to a powerful Alpha machine in future for those departments demanding very high computing power.
Currently, the Pentium PC is chosen as the standard server machine because this configuration has numerous advantages as listed below :

Its price is only about half that of an Alpha machine.
The development pace of PC-technology is much faster. For instance, it can be transparently switched to a more powerful CPU (like Pentium Pro ("P6"), "P7") and faster disks once the products are available.
Due to the huge number of Pentium PC suppliers, more choices are available and better bargain for the machines and peripherals can be obtained.

In view of all the relative advantages discussed above, CSC has chosen Windows NT Server running on a Pentium PC as the standard departmental network server software platform.

Acknowledgments

Most information is provided by Mr. CY Kwok, Mr. Manfred Chan, and Mr. CT Tam. They are members of the Pathworks Task Force in CSC.

Notes:

LAN Manager (also called "OS/2 LAN Manager") is a Network Operating System from Microsoft, the original function is to expand the features of OS/2 enabling computers to join a LAN. Microsoft has licensed LAN Manager to vendors like IBM (LAN Server) and DEC (Pathworks), who made their own enhancements and modifications. That is why Pathworks V5 is compatible to it.
DECnet is the proprietary protocol stack of Digital for networking.
LAT (Local Area Transport) is a LAN-base protocol for host connection.
Domain is a combination of servers and workstations that are grouped to create an administrative unit. In our configuration, we have one domain for each department/division.
Group is a set of users who share common permissions for one or more resources.
Local Group is used to grant permissions and rights only for the servers of its own domain. LAN Manager V2 does not support local groups.

Computing Services Centre

City University of Hong Kong
ccnetcom@cityu.edu.hk