Previous | Table of Contents | Next |
Measuring the performance of your server will take you into an uncharted wilderness if you try to pick a single point for comparison. The performance of your server should not be based on the speed of your processor, network adapter, or the I/O subsystem. Instead, your servers performance should be based on how well the system serves its clients. If your clients are experiencing delays while working from a network drive, you can identify the cause of the delay and solve it. If you examine all the possibilities, you might find that the delay your clients are experiencing is not caused by the server at all.
Consider the following as a possibility. You have 1 server and 10 network clients. All the clients are accessing a shared copy of Windows 95 on the server. In low memory situationspretty much a given for a Windows 95 computer performing any real workWindows 95 loads and unloads operating system components at a rapid rate. All of these computers are using a 10 Base-T network. The theoretical maximum possible bandwidth of your network is 10Mb/sec. This means that all your clients together share the 10Mb/sec. bandwidth. During simultaneous use, your clients would then each have a 1Mb/sec. pathway to the server. Right? Even though this is what many people believe to be true, in actuality, it is not true.
An Ethernet network is based on the Carrier Sense Multiple Access With Collision Detection (CSMA/CD) model. All network adapters transmit/receive data at 10Mb/sec. If two network adapters transmit at the same time, this is called a collision. The network adapter will detect a collision and pause for a random time before retransmitting. The more network bandwidth that is in use, the more likely collisions will occur. When approximately 80 percent of the theoretical maximum bandwidth is in use, your network will collapse due to the number of collisions detected. This is why most network administrators segment their network subnets whenever 50 percent of the network bandwidth is reached.
In this example, you could fire up the Performance Monitor, the Network Monitor, or other hardware-based network analysis tool. You might determine that a high percentage of your network bandwidth is in use and multiple collisions are occurring on a frequent basis. The solution to improve network performance might be to replace the 10 Base-T network on the server with a 100 Base-TX network adapter. You can connect the 100 Base-TX network card to a 100 Base-TX/10 Base-T switch instead of a 10 Base-T hub. Your clients can then be connected directly to the switch using their existing 10 Base-T network adapters.
The network will then be segmented so that each network pathway is completely isolated from the other. Your network clients will have a 10Mb/sec. pathway to the switch, and the server will have a 100Mb/sec. pathway to the switch. This will basically give each client a pathway to the server at 1/10 of the bandwidth of the servers connection to the switch. A switch can be used to share bandwidth, unlike a hub. This should improve the clients perceived performance, but will then expose other areas that need to be considered.
TIP: If your network cards and switch support duplexing, you can double your network throughput. By enabling duplexing on both the cards and switch, you can achieve 20 Mb/sec for the clients and 200 Mb/sec for the server.
The key item in the preceding example is that you isolated a specific problem (poor client response time) by measuring the performance of a specific component (network bandwidth) to determine how well it was performing. Having determined the cause (overworked network), you found a solution (segment the network). This is exactly how performance measurements are made in the real world. You start with a big picture and narrow it down to a specific instance. The big picture, however, should always be based on your network clients. Solve your clients problems, and they will never complain about the performance of your server. If you can prevent their problems before they happen, this is even better.
Previous | Table of Contents | Next |