Considering the move to NT?
- By Shawn McCarthy
- Oct 30, 1995
Is your office rehosting legacy applications to Microsoft
Corp.'s Windows NT environment?
If so, you're not alone. Like their private-sector counterparts, government systems
professionals are choosing Windows NT as their client-server platform and then confronting
hundreds of issues, big and small, associated with the move.
But federal decision-makers have a special challenge on their plate. They must decide
whether they want a Unix application to remain a Unix application or become a Windows
application with Win32 support.
Many federal sites are required to use Posix, and Windows NT is approved as a
Posix-compliant operating system, as specified in Federal Information Processing Standard
151-2. But the choice is not that simple.
"As a programmer, the services specified in FIPS 151-2 is really a very limited
subset of the common Unix system services," said David Solomon, a consultant who,
through his David Solomon Seminars company, teaches VMS and mainframe customers about the
NT platform. "The FIPS is just services for basic file I/O, process creation. That
spec doesn't include services for the network or many things that a "real"
application must do."
The problem in not unique to NT ports, Solomon said. "Many programmers find that
FIPS 151-2 by itself is not terribly useful as a programming subset," he said.
If you are moving a Unix app, it probably already uses services that fall outside of
FIPS 151-2. It's unusual to find an application that limits itself just to what is
supported in the 151-2 spec.
Thus, if you're porting a Unix app to NT and you want full functionality, you may not
have any choice except to recompile it as a Win32 application for operation on NT. The
Win32 subsystem allows the larger set of services--such as creating a window, networking
and multithreading--to work.
And while NT supports multiple file systems that can reside on different parts of a
disk (including the DOS file allocation table and OS/2 file system), NT's security
requires use of the NT File System (NTFS). This affects the port.
If adding value is the agency's main reason for rehosting, a Win32 port could be the
best solution. But if Posix compliance is paramount and you want to maintain an open
system, moving to NT may not be the best choice because its limitations, according to
specialists at the National Institute of Standards and Technology.
If you do choose to port to NT, you have two routes, Solomon said. One is to replace
the system service calls you're making on Unix with appropriate calls to Win 32. Most
calls in one system have a parallel in the other.
Or you can buy a Unix porting library like the Nutcracker family of porting tools from
DataFocus Inc., Fairfgax, Va. These tools let you recompile your Unix C code directly into
Win 32 applications.
At least one federal shop has encountered a second NT-related problem, now that it has
considerable experience with the OS. Once you rehost on a Windows NT server, you may find
it suffers from the same disk fragmentation problems that have plagued Digital Equipment
Corp. OpenVMS systems for years.
Many people don't realize that when Microsoft started its NT development, it hired many
of the DEC engineers who had worked on the VMS operating system. Windows NT's design
borrows heavily from VMS for many of its system management functions, especially memory
management and input/output structure.
Like the hard-drive file fragmentation found on most systems, fragmentation with NT
occurs because the disk fills with files, and the new files are broken up to fill vacant
space. Unfortunately, MS-DOS and Windows defragmentation tools like Symantec Corp.'s
Norton Utilities aren't designed for the NTFS file system. Also they don't handle the
longer file names found on NT.
"There's a significant difference in operation between fragmented NT File System
partitions and unfragmented NTFS partitions," said J. Brisco Stephens, advanced
science information systems coordinator at NASA's Marshall Space Flight Center in
Huntsville, Ala. "It's something we did not recognize until we had extensive
experience with NTFS."
Stephens noticed increased file loading times and eventually a 50 percent loss in
performance. He dealt with the problem by occasionally stripping everything from his disks
and rebuilding the system, which took at least a half-day.
He finally installed a Windows NT version of Diskeeper, a popular VMS defragmentation
utility from Executive Software International Inc. of Glendale, Calif. Diskeeper works in
the background, during idle CPU time, moving pieces of files around to close up the holes.
Versions are available for most platforms that run a version of NT. The list price is
$199 for the workstation version and $399 for the server version. Diskeeper also is
available on the Coast Guard's Standard Workstation III contract held by Unisys Corp.
Shawn McCarthy, a former writer for GCN, is senior analyst and program manager for government IT opportunities at IDC.