Timothy
Parker Consulting Incorporated
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Windows
NT 4: A Critical View What
does Windows NT 4.0 have to offer you? Is
it worth upgrading from Windows 3.51? Those are the questions many Windows NT users will be asking
themselves in the next few months, and apart from the Microsoft promotional
literature there are few solid answers available. That’s why we undertook a critical comparison of the new
version of NT against the older 3.51 version.
While it may be inevitable that we all will move to Windows NT 4.0 as
support for 3.51 is terminated, the decision of when to move and what effects
the change will have on us can alter the timing of the upgrade.
Windows
NT 4.0 has been available in beta format for almost a year, with the shipping
version finally released in October. The
author has worked with beta versions for eight months (completing several book
updates for Sams Publishing) and with the shipping version since before its
commercial release. During that
time, a number of performance tests as well as several observations on the
behavior of the new version of NT have been made, and summarized here.
In all cases, tests and observations are based on the final shipping
version of NT 4.0 Workstation and Server. Microsoft
is proud of their new release of Windows NT, and has a mass of literature
showing off the new operating system’s highlights and features.
Passing through the cosmetic changes and the press euphoria of the
release to the nitty-gritty can be difficult, especially since many kernel
parameters are hard to measure and assess independently, so some reliance on
Microsoft’s official descriptions and measurements must be used.
Wherever possible, though, we’ve tried to examine each aspect of the
new operating system independently. The
changes to the operating system can be best summarized as a set of points, which
we’ve done in the sidebar “Windows NT 4.0 Overview”.
Most of these items are self-explanatory, but several are examined in
much greater depth later in this article. We
can start by looking at a few of the more important aspects of Windows NT 4.0:
its architecture changes and the performance improvements. Architectural
Changes and Performance Microsoft
claims to have redesigned and reengineered their Windows NT operating system
architecture for version 4.0. A
look at the size of the programs on CD shows that much of the operating system
is smaller, and first impressions of the operating system are that it is faster,
too. The
core component of the operating system is the Windows NT Executive, which
contains the microkernel, hardware abstraction layer (HAL), and most executive
services such as virtual memory management, security monitor, and process
managers which sit on top of the microkernel.
The microkernel itself is responsible for task scheduling and management,
and is removed from the hardware and its components including timers,
interrupts, and I/O handling through the HAL. A
major change for the Executive with NT 4.0 is the addition of a Win32K Executive
as a layer sitting parallel with the microkernel and HAL, directly accessing the
hardware. The Win32K Executive
houses many of the Windows APIs, including the window manager, Graphics Device
Interface (GDI), and device drivers for the GDI.
In earlier versions of NT, these APIs sat in the Win32 subsystem. The
microkernel of Windows NT 4.0 has been updated to allow handling of threads much
better, as modern processors provide several privilege levels for threads.
Code running at one privilege level cannot access memory locations used
by code with a higher level. The NT
Executive itself runs at the highest privilege level, called “kernel mode”.
An Intel CPU, such as the 80486 and Pentium, supports four privilege
levels, called ring 0 (highest) through ring 3. Ring 0 is kernel mode. Ring
3 (the lowest setting) is where applications and user-oriented processes are
executed. This prevents user
applications from accessing data and memory addresses with higher levels,
including the Executive, so a crash by an application leaves the Executive code
unaffected. (Windows 95 does not
implement this architecture, even though it is better designed than Windows
3.11, so an application crash can crash the entire Windows 95 operating system.) As
with previous versions of NT, Windows NT 4 runs each application as a separate
process. A dedicated address space
is allocated to each process, so errors and crashes in that application should
leave the rest of the system untouched. When
one application has to interact with another, the Executive ensure there is
proper separation between the processes to prevent cascade crashing.
Windows NT’s reliability is born out of this design.
In several months of working with the new operating
system through four beta releases, the author had a single system crash.
In all other cases, applications crashed regularly, but the operating
system continued to work. With the
shipping version, no crashes have been encountered in four weeks of heavy usage
and testing. Memory
is handled slightly differently with NT 4.0.
The operating system now maps the Win32 API code into the address of
every process, so there are no shared memory buffers or server threads involved.
The use of this technique means that the GUI shell code has increased in
size, through, although this doesn’t seem to have an effect on performance.
The removal of shared buffers and server threads reduces an Executive
bottleneck as well as improves reliability for each application.
With less memory used by each application, the overall system memory
usage is reduced for the same application load over NT 3.51. One
aspect of the redesign of the kernel that Microsoft had to pay special attention
to is security. The previous
releases of NT reached C2 security levels.
The redesign doesn’t seem to have compromised that security level at
all. The security system
implemented for NT 4.0 is very similar to that in 3.51, and since the security
system is still a part of the Executive there is likely to be no major change in
security handling. Windows
NT 4.0 Performance If
Windows NT 4.0 faster than earlier versions?
In a nutshell, yes. The
redesign of the operating system and the rewritten code make for a slightly
faster operating system across the board, although the sheer overhead of the
operating systems and its multiple API layers means that Windows NT 4.0 is not
as fast as Windows 95. Most people
wouldn’t expect it to be, either, as Windows 95 is much simpler in design and
purpose. By
locating the window manager in the kernel, Microsoft removed a big bottleneck
that existed with NT 3.51. This was
especially a problem when multiple applications had to call the window manager
frequently, and caused slowdowns in the operating system.
With the relocated window manager, the bottlenecks seem to have been
removed. Visually,
Windows NT 4.0 is faster to refresh and redraw the screen, mostly due to the
Win32K Executive housing the GDI. Since
the GDI can talk directly to the video hardware and runs in the ring 0 protected
space of the Executive, it is fast and virtually crash-proof.
Applications can talk directly to the GDI, which removes several layers
of drivers and switchers that were involved with NT 3.51.
The result is faster graphics. A
few simple benchmarks show that the NT 4.0 system handles graphics an average of
17% faster than the earlier NT 3.51 did.
There is one potential problem with this approach: a faulty or buggy
video driver could, in theory, crash the entire operating system (whereas with
NT 3.51 is could only crash the Win32 subsystem).
Microsoft recognizes this potential problem, hence the certification
program for device drivers they have instituted.
After all, the reliability of any operating system is largely dependent
on the quality of the device drivers it uses. Network-oriented
tasks are faster with NT 4.0, too. The
most obvious change is in the File and Print Sharing features, which are almost
twice as fast as those in NT 3.51. Part
of this speed improvement is the redesigned kernel, and the rest is probably
from the streamlined utilities and networking.
For network printing tasks, Windows NT 4.0 shows an immediate improvement
in queuing and printing over 3.51. File
sharing has improved for NT 4.0 in a number of ways. The inherent improvements of the kernel design and utilities
has helped speed transfer, but there is also a potential performance increase
that 3.51 could not offer through the new network drivers. NT 4.0 supports several of the newer high-speed networking
protocols such as Fast Ethernet and 100VG AnyLAN, both offering up to 100Mbps.
When connected to a 100Mbps network, the NT 4.0 drivers can take
advantage of the network through a smaller number of frames transmitted, fewer
interrupts to the network interface card, and better cache handling.
Network
printing has improved primarily because print requests are now rendered on the
server instead of through the application.
This results in a faster return to the calling application (no more
waiting for the print request to be formatted before regaining control of the
cursor). Windows NT 4.0 allows all
shared printer device drivers to be located on a server instead of spread over
all the clients, which minimized upgrade problems to one machine and allows
better installation routines. The
Print Manager of Windows 3.51 has been replaced by individual printer folders in
4.0, which show the current status of all local and remote printers more
accurately. A
quick comparison of the NT 4.0 versus 3.51 versions on the author’s HP-based
100VG AnyLAN network (with maximum measured transmission rates of 90Mbps) shows
that the NT 4.0 system can sustain a transfer rate for files double that of 3.51
(peaking at 83Mbps). Also, analysis
of the network traffic with a data analyzer shows that the retransmission rates
of packets are much fewer with 4.0 than 3.51, obviously due to better
optimization of the network drivers. One useful feature of Windows NT 4.0 Server is the
ability to have it act as a router, providing interconnection between networks
of different protocols. Running
standard benchmarks such as TPC-A and TPC-C shows the performance difference
between 3.51 and 4.0 in a database environment. (TPC-A and TPC-C both measure transaction processing times
but TPC-C adds multiple transaction types and more complex database operations.
The TPC-C benchmark is supposed to represent realistic transaction behavior for
most transaction-based applications.) The
TPC-C benchmark was measured by the author on a single processor Pentium 150mhz
machine with 64MB RAM running Windows NT 4.0 and Microsoft’s SQL Server 6.5.
Although time constraints prevented rigorous testing, the Windows NT 4.0
server offered one quarter more transactions per minute than the Windows 3.51
machine. Microsoft has published
similar values for a Compaq ProLiant 4500s system with four 133Mhz Pentium
processors, 1GB RAM and dozens of disk drives.
They measured 2500tpmC (TPC-C transactions per minute) for Windows 3.51
and 3600tpmC for Windows NT 4.0. The
Windows NT 4.0 setup resulted in just under 50% more transactions per minute
than the older Windows NT version. The
use of multiprocessor machines is an additional facet of Windows NT 4.0 that has
been enhanced over the earlier version. Windows
NT 4.0 supports full symmetric multiprocessing on systems with up to 32
processors. While this type of
configuration is very unlikely on a PC-based system because memory bus
saturation occurs very quickly above four processors, for DEC Alpha, MIPS, and
PowerPC systems the use of multiple processors is now better handled. Hardware
Requirements Hardware
requirements have changed slightly for NT 4.0.
Essentially, the 80386 chip is no longer supported (although few users
ran NT 3.51 on 80386s anyway). Microsoft
recommends a fast 80486 or Pentium Intel chip, or one of the RISC machines
supported. Since the majority of
machines running NT are Intel-based, we will concentrate on that platform.
The minimum suggested memory for NT 4.0 Workstation is 12MB, and 16MB for
NT Server. These should be
considered bare minimums, with 32MB better for both platforms.
Heavily-used servers will require at least 64MB and preferably more to
provide best performance and avoid a lot of swapping. On most Intel platforms, the limiting factor for performance
will be the motherboard and memory bus speeds. NT
4.0 supports Pentium and Pentium Pro processors through optimization for their
larger memory pages and pipelines. A
new cache algorithm is supposed to reduce the churn in the cache, but our tests
could not evaluate this directly. Part
of the improvement in caching is, according to Microsoft, due to the use of
larger timeslices for applications, resulting in fewer paging operations and
cache replacements. As mentioned
already, multiprocessor support has been expanded to provide up to 64 CPUs at
once. Earth
Calling Mars Communications
and network support has been modified noticeably with the latest release of NT.
The improvements in Fast Ethenet and 100VG AnyLAN support have already
been mentioned. Support for PPTP (Point to Point Tunneling Protocol) has been
added to allow public networks (including the Internet) to act as virtual
private networks. PPTP is an
encapsulation method for packets that allows other protocols to be encapsulated
in TCP/IP datagrams. PPTP also
provides much better security that PPP. Using
PPTP with the enhanced RAS subsystem allows better remote access to an NT 4.0
server and network. While
on the subject of RAS (Remote Access Service), Windows NT 4.0 has enhanced RAS
support considerably. The version
of RAS included with NT 4.0 allows full PPP channel aggregation, which means
clients dialing into a server can combine multiple data lines for higher
throughput (instead of being forced to use a single channel, as with NT 3.51).
This allows users on the road with multi-channel capable models (such as
ISDN modems) to use two lines instead of one for better throughput.
RAS even allows mixed bonding of lines, so two ISDN and two analog lines
could be combined for throughput to a single client, for example.
While this won’t be used by most people, this feature does allow for
much better throughput to clients in some situations such as remote
demonstrations. Networking The
biggest improvement in Windows NT 4.0 networking is the inclusion of DCOM
(Distributed Common Object Model). DCOM
allows developers to use a common component library across a network.
This reduces application size and provides better upgrade paths as
components change. A DCOM-equipped
application communicates with the object library server over a network to obtain
the objects it needs. WINS
and DNS as now more tightly integrated. The
DNS service provided with NT 4.0 has been completely rewritten, and now includes
a GUI-driven front end for administration (a very nice touch over the older
method). Integrating WINS and DNS
allows clients to use DNS compound names across a WINS network, instead of
having to handle two different naming methods. For
NetWare users, NetWare Directory Services has been included in the new NetWare
client. This provides for better
authentication and printing with DNS. Login
script processing has been added to NT 4.0, something that was sorely missed by
users of NT 3.51. Finally
on the network front, Windows NT 4.0 allows diskless Windows 95 workstation and
clients to be booted straight from the server using Remote Program Load (RIPL).
This is a feature that many users have asked for.
It allows Windows NT 4.0 networks to catch up a little in the race
against UNIX, which has long support diskless booting. IIS
Part of the Package The
bundling of the Internet Information Server (IIS) is an important addition to
Windows NT 4.0 Server. Previously,
IIS had to be purchased separately, but the newly bundled version has been
enhanced and now better integrates with NT’s directory and security
structures. IIS offers a number of
intranet and Internet utilities such as a Web server, FTP server, and support
tools. Although Microsoft claims
IIS is the fastest Web server on the market, our testing shows that while the
version of IIS included with Server 4.0 is much faster than the older IIS
version 1.0 that was an add-on, it does tend to fall behind some commercial Web
server applications under load. The
performance of IIS under 4.0 is noticeably faster than under 3.51.
In a single-processor test using a Pentium 150mhz CPU and 64MB RAM, IIS
transaction handling runs twice as fast under 4.0.
This speed increase allows not only more transactions to be handled (and
hence more user load) but also a much better performance for the user,
especially on intranets. The
version of IIS supplied with NT 4.0 Server includes FrontPage, a WYSIWYG Web
page designer that generates HTML code for IIS, as well as a copy of Internet
Explorer 2.0 (an update to Explorer 3.0 must be downloaded from the Microsoft
Web site; you would have expected Microsoft to bundle it with more recent
shipments of NT 4.0, but they don’t).
Also available for IIS is the Index Server (which must also be downloaded
from the Microsoft Web site). The
Index Server indexes text and files to provide better search capabilities. A
full description of IIS is beyond the scope of this article.
It is sufficient to point out that the inclusion of IIS with NT 4.0
Server is likely to spur the proliferation of intranet Web sites on most
networks, as well as make Internet Web site servers slightly more reasonable
financially for smaller companies. The
GUI Issue A
typical user will notice a number of changes to Windows NT 4.0, not the least of
which is the new GUI. Traditional
items like the Print Manager, as mentioned earlier in the section on
Performance, have been replaced with individual folders for each printer.
Also, users will find that after a print request they regain control of
their applications much faster with 4.0 since the server now handles the print
request rendering. One
of the most touted aspects of Windows NT 4.0 is the new GUI, patterned after the
GUI used in Windows 95. Most of the
Windows 95 elements are there: the task bar at the bottom of the screen, the
Start menu and divisions into applications and controlling elements, the desktop
layout, and the overall look and feel of the interface.
The mouse right and left buttons bring up menus very similar to Windows
95, with the content of the menus depending on where the mouse is positioned. The
Windows 95 GUI was intended to much more user-friendly than the older Program
Manager appearance of Windows 3.11 and Windows NT 3.51.
Most novice users haven’t found the Windows 95 interface significantly
easier or better than the older GUI, but Microsoft seems committed to the new
look-and-feel. The adoption of the
Windows 95 GUI for Windows NT 4 isn’t based so much on the need to provide a
simple interface (few beginners are likely to use Windows NT Workstation or
Server instead of Windows 95) as to legitimize the Windows 95 interface design
and provide a consistent operating system look and feel for the Microsoft
product lines. With the replacement of Windows NT 3.51 the older Program
Manager type of GUI is now officially passed, according to Microsoft.
If
the new GUI easier to use for Windows NT Workstation and Server?
Despite Microsoft’s insistence, most workstation and server users will
find the new interface a little more awkward than the older Program Manager
system. With the older GUI you
could arrange windows in the Program Manager to suit your specific needs, with
every application and utility a simple double-click (or for Logitech mouse
users, a middle mouse button click) away. No
opening new windows, and no hunting for icons.
With the Windows 95 GUI, applications have to be launched through the
Start button’s labyrinthine hierarchy. On
a heavily application-loaded system, the menus that have to be waded through can
be four or five levels deep. This
makes launching (and even finding) the right icon much more time-consuming and
annoying. Windows
NT does allow you to make shortcuts on the desktop for the most important tasks,
and most users will find this the best way to handle frequently-used
applications. However, the desktop
quickly becomes cluttered and difficult to keep organized when many shortcuts
are created. The
new Windows 95 interface does have some advantages, of course.
It allows better design of nested menus from the Start button than you
could manage with Windows NT 3.5 or Windows 3.11.
You can sub-menu unimportant or less-often used applications, leaving
them out of the way until needed. There’s
also the important aspect of having a consistent look-and-feel with Windows 95,
especially in mixed environments where some users will have Windows 95 systems
and others will have Windows NT. Eliminating
most of the visual cues to the Windows NT environment will make moving from
Windows 95 to Windows NT easier for users, as well as providing a better
application look across the platforms. The
Task Manager has been greatly updated from that of 3.51.
It resemble the Task Manager of Windows 95, and can give detailed
information about each process on the system.
Accurate measurements of the amount of memory and CPU cycles each
application is using help users determine when memory or CPU hogging
applications are running. Termination of applications through the task manager is
almost always successful. APIs Windows
NT adds several new APIs designed to provide better performance.
One of the new APIs is aimed at optimizing fibers (non-preemptive
threads). By using the fiber API
application developers are able to set up specific scheduling models for their
application’s components. The use of fibers should also help in the porting of Windows
NT developed applications to other platforms. As
you would expect, there is the usual raft of Microsoft APIs, including TAPI
(Telephone API) 2.0 which allows better computer-telephone integration (CTI).
TAPI allows an NT 4.0 server act as a voice-and-data handler, including
applications such as interactive voice response and call handling centers.
In addition, TAPI 2.0 provides better integration with existing telephone
PBXs and switches. A
new encryption API has been added to Windows NT 4.0. This offers developers the ability to use the API’s
encryption methods over non-secure networks such as the Internet, as well as in
secure networks. With electronic
fund handling and sensitive data transmission increasing in use dramatically,
the encryption API will be useful for many application developers who have used
third-party commercial solutions to this point. Summary Is
Windows NT 4.0 a significant improvement over 3.51? Undoubtedly, yes. There
are enough modifications in the underlying behavior of the kernel, user
utilities, and system administration tasks to make the upgrade very tempting.
There is no forward compatibility problem with 4.0, and while the change
in GUI will throw many die-hard Windows 3.X and Windows NT 3.5X users for a
while, the performance improvements, better networking, and extended features
make 4.0 a must-have for all users. Performance
improvements are not the driving item for most NT server and workstation users,
although they do add up with 4.0. In
general, our test systems responded anywhere from 10 to 25% faster in all daily
use tests. It was the little
performance changes, especially printing and network access, that made the most
impression on us initially. Although
we have not tried a multiprocessor system, NT Server’s performance boost there
is significant according to Microsoft’s numbers, and that will make 4.0 a much
better transaction processing or Web site server machine. The
robustness of NT 3.51 and its security features have all been carried over to
4.0, making it a better designed version of the popular 3.51 operating system.
There’s very little not to like about NT 4.0.
We’re not really big fans of the Windows 95 GUI, but that’s a minor
quibble for most people. Underneath
the GUI, though, NT 4.0 is a new operating system, and one we highly recommend. ************************************ Sidebar:
Windows NT 4.0 Overview What’s
new? In a nutshell, these are the
changes and additions to NT 4.0 versus the earlier 3.51 release.
In some cases, these points are expanded on in the main article.
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