- Chapter 5 A Step-By-Step Approach to Capacity Planning in Client/Server Systems
- 2 Adequate Capacity
- 3 A Methodology for Capacity Planning in C/S Environments
- 4 Understanding the Environment
- 5 Workload Characterization
- 6 Workload Forecasting
- 7 Performance Modeling and Prediction
- 8 Development of a Cost Model
- 9 Cost/Performance Analysis
- 10 Concluding Remarks
- BIBLIOGRAPHY
5.4 Understanding the Environment
The initial phase of the methodology consists of learning what kind of hardware (clients and servers), software (operating systems, middleware, and applications), network connectivity, and network protocols, are present in the environment. It also involves the identification of peak usage periods, management structures, and service-level agreements. This information is gathered by various means including user group meetings, audits, questionnaires, help desk records, planning documents, interviews, and other information-gathering techniques [7].
Table 5.1 summarizes the main elements of a C/S system that must be catalogued and understood before the remaining steps of the methodology can be taken.
Table 5.1 Elements in Understanding the Environment
|
Element |
Description |
|
Client platform |
Quantity and type |
|
Server platform |
Quantity, type, configuration, and function |
|
Middleware |
Type (e.g., TP monitors) |
|
DBMS |
Type |
|
Application |
Main types of applications |
|
Network connectivity |
Network connectivity diagram showing all LANs, WANs, network technologies, routers, servers, and number of clients per LAN segment |
|
Network protocols |
List of network protocols being routed. |
|
Service-level agreements |
Existing SLAs per applications. When formal SLAs are absent, industry standards can be used (see[4]) |
|
LAN management and support |
LAN management support structure, size expertise, and responsiveness to users |
|
Procurement procedures |
Elements of the procurment process, justification mechanisms for acquisitions, expenditure limits, authorization mechanisms, and duration of the procurement cycle |
An example of the outcome of the Understanding the Environment step for the C/S of Fig. 5.3 would be as follows.
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Clients and servers. The network consists of four LAN segments (three 10 Mbps Ethernets and one 16 Mbps Token Ring) interconnected through a 100 Mbps FDDI ring. LAN 3 is connected to the Internet. LAN 1 has a Windows NT-based server and 120 Windows NT-based PC clients. LAN 2 has a RISC-type Unix server and 50 Unix workstations. This file server uses a storage box with several
Figure 5.3. Example C/S system for capacity planning methodology.
RAID-5 disks and a capacity of 512 Gbytes. LAN 3 runs an ftp proxy server, a telnet proxy server, a Web proxy server, and the e-mail server on a Windows NT server-based dual processor high-end PC-based machine. This LAN supports 100 Windows NT clients. Finally, LAN 4 has a Windows NT-based file server and an SQL database server running Oracle to support enterprise-wide mission-critical applications. This LAN has 100 Windows NT-based clients. BEA's Tuxedo [1] is used as a Transaction Processing (TP) Monitor to support client/server transaction management.
Applications. Workstations on LAN 2 are mostly used by researchers of the R&D department engaged in running computer simulations of molecular biology experiments. These researchers store all their files in the file server in LAN 2. They use e-mail, ftp, telnet, and Web services from the proxy server on LAN 3. Clients on LANs 1, 3, and 4 split their time between running office automation applications (e.g., word processing, spreadsheets, and presentation preparation packages) and running various types of client/server transactions to support sales, marketing, personnel, accounting, and financial activities. These C/S transactions use a TP monitor and the SQL server on LAN 4. All users in LANs 1, 3, and 4 read e-mail and access the Web through the proxy server on LAN 3. The company's employees go through Web-based training courses hosted at the server on LAN 3. Most of the accesses to these applications come from clients on LANs 1, 3, and 4. Network connectivity and protocols. The network connectivity map is given in Fig. 5.3. The Internet and transport protocols used throughout all networks is TCP/IP.
Service-level agreements. There are no formal SLAs established, but users start to complain if response times exceed 2 sec for trivial C/S transactions and 5 sec for the more complex transactions. Response times at e-mail and Web services has not been a problem.
LAN management and support. Each of the four user LANs (LANs 1{4) have a dedicated team of LAN and system administrators. The number of system administrators for each of these LANs is 6, 3, 5, and 6, respectively. There is also a Database Administrator (DBA) for the database managed by the SQL server and three network specialists that constantly monitor the performance on the FDDI ring and are responsible for overall network management functions such as assigning IP addresses to subnetworks, managing routing tables, maintaining network security, and verifying the connection to the Internet.
Procurement procedures. As an example, procurement decisions could be made by an Information Technology Committee, headed by the Chief Information Officer (CIO) of the company and composed of four user representatives and four system administrators (one from each LAN), which reviews applications for hardware and software upgrades. Decisions are made based on budget availability and on how well the requests are justified. The average procurement cycle for items over $5,000 is 2 mo. Expenditures below $5,000 can be made using a much faster procedure that takes two business days on the average.