System Architecture Design for GIS
The Reliant conversion project started with one major GIS operation consisting of 17 service
centers surrounding metropolitan Houston, multiple remote gas service centers, plus a main core
of users, digitizers, administrators, and management in downtown Houston. One of the GIS
operational systems being replaced ran on Sun Solaris and was programmed in-house. Remote
users were able to access the UNIX database using Exceed’s X-emulation package. UNIX and
Novell printers were managed with JetDirect software. Users required UNIX accounts, printers,
and so forth.
The next major GIS operation being converted consisted of six operating divisions in Texas,
Louisiana, and Mississippi. This system also included a main core of users, digitizers, and
management in downtown Houston. There were also some additional digitizers and users
distributed in the six operating offices across three states. The operating platform for this
implementation was Windows NT 4.0.
The GIS conversion project goal was to merge these two systems into one common GIS
environment. There were additional challenges, as some of the existing users were located at
remote sites over very slow wide area network communication links. These links ranged from
128 Kbps to 256 Kbps and a partial T-1. User needs included requirements for editing, viewing,
and printing without incurring enormous infrastructure upgrade costs.
The GIS vendor had some interesting ideas on how to achieve some of the major parts of our
tasks. Several other vendor clients had experienced success with thin-client architectures, and
Reliant was provided some best practices for implementing this technology. The vendor had
established hardware configuration guidelines to support Windows Terminal Server with Citrix
MetaFrame running on Microsoft Windows 4.0 Terminal Services Edition. Citrix had
established a very good track record supporting GIS implementations with the Windows NT 3.51
Winframe server product, providing a good reason to believe the Windows NT 4.0 version would
be even better.
A local Citrix VAR provided some initial test software. Initial performance testing was
conducted using a beta version of the Windows NT 4.0 version of Windows Terminal Server.
The local Microsoft sales force provided beta CDs in order to set-up the original test bed.
Compaq servers were used to conduct initial WTS testing in the Reliant Energy network
environment. Initial WTS tests were supported by FDDI backbones and Token Ring local area
networks. Since that time, much of the Reliant infrastructure has shifted to switched 100BaseT.
Initial testing using traditional file-based data sources provided enough information to prove that
the Citrix ICA architecture would be sending fewer packets across the wire than a traditional
client/server or Microsoft’s RDP protocol. This established information supporting Citrix
MetaFrame on Microsoft Terminal Server as the choice configuration for production
deployment.
The next deployment phase included plans within budget to ramp up support to 75 users.
Compaq 6500 four-CPU 500-MHZ servers were purchased based on test results suggesting each
platform could comfortably support 25 users. Three servers were purchased and configured in a
farm configuration to support the initial 75 users. The current operational experience validates
the initial sizing projections. Based on these results, Microsoft Terminal Servers and Client
Access Licenses along with the Citrix Metaframe and load-balancing software were purchased to
support the production system. In the winter of 1998, a complete WTS production configuration
was established to support the huge data conversion project then underway.
The data conversion plan was scheduled to go live with the first databases on May 1, 1999.
Shortly after that go-live date, the central system had to be able to provide remote users access to
the databases, distribute Citrix client software, set up printers on the terminal server, publish
applications and, in the end, support production performance requirements.
Remote GIS users were located in division offices in New Braunfels and Jacksonville, Texas,
New Iberia, Louisiana, and Brandon, Missisippi. Representatives from each of those locations
were brought to Houston and provided with GIS training. Representatives returned to their
remote locations with CDs containing the Citrix client software to install at their home sites.
Support Desk personnel followed up later with on-site visits, but in the early stages, local
representatives at the remote sites supported the initial install of the software to get things going.
The initial ramp-up time consisted of a few months, demonstrating positive progress toward a
distributed environment that provided users the ability to update their data from remote sites.
The deployed configuration supported all production databases located in Houston with
centralized administration and backup. Remote sites were provided a local replicated database
that would be used for printing only. (Citrix software supports printing to local printers at the
remote location. This was not implemented since development tests showed that one plot over a
128-Kbps WAN segment saturated that line for over 10 minutes. Remote clients included both
GIS and SAP users who shared limited WAN bandwidth, so batch plots over these lines were not
recommended in the production configuration.) The remote sites databases were updated from
the central database in Houston using Lakeview Technology OmniReplicator software. Remote
site databases were housed on Compaq M370 single-CPU servers running Windows NT 4.0,
including two 36-GB mirrored disks for the OS and database environments. The users were
shown how to connect via Citrix to Houston to edit their data. Users accessed local databases
using locally installed GIS software to support plotting requirements.
Concurrent users supported by the Windows Terminal Server environment have continued to
increase since the initial implementation. Sixty to 70 concurrent Citrix editors are supported by
central WTS servers during peak work periods. (Total user count is currently 140 to 150 GIS
users). Production shifts run from 6:00 am to 2:00 pm. Current usage does not show that our
servers are stressed, validating that the right hardware choices were made, walking the fine line
between overkill and underspend. The current environment has the capacity to handle peak
loads, consistently receiving good reports from users on system response. When users
experience good response time, they seem to have a more positive attitude, which increases
productivity. After almost two years of production, the original servers continue to provide
quality performance.
