Red Hat ENTERPRISE LINUX 4 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

Also see for ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE: Installation guide Installation guide Tuning guide Installation guide Manual

Contents

Chapter 3. Bandwidth and Processing Power 333.1.4. Potential Bandwidth-Related SolutionsFortunately, bandwidth-related problems can be addressed. In fact, there are several approaches youcan take:• Spread the load• Reduce the load• Increase the capacityThe following sections explore each approach in more detail.3.1.4.1. Spread the LoadThe first approach is to more evenly distribute the bus activity. In other words, if one bus is overloadedand another is idle, perhaps the situation would be improved by moving some of the load to the idlebus.As a system administrator, this is the first approach you should consider, as often there are additionalbuses already present in your system. For example, most PCs include at least two ATA channels(which is just another name for a bus). If you have two ATA disk drives and two ATA channels, whyshould both drives be on the same channel?Even if your system configuration does not include additional buses, spreading the load might still bea reasonable approach. The hardware expenditures to do so would be less expensive than replacing anexisting bus with higher-capacity hardware.3.1.4.2. Reduce the LoadAt first glance, reducing the load and spreading the load appear to be different sides of the same coin.After all, when one spreads the load, it acts to reduce the load (at least on the overloaded bus), correct?While this viewpoint is correct, it is not the same as reducing the load globally. The key here is todetermine if there is some aspect of the system load that is causing this particular bus to be overloaded.For example, is a network heavily loaded due to activities that are unnecessary? Perhaps a smalltemporary file is the recipient of heavy read/write I/O. If that temporary file resides on a networkedfile server, a great deal of network traffic could be eliminated by working with the file locally.3.1.4.3. Increase the CapacityThe obvious solution to insufficient bandwidth is to increase it somehow. However, this is usually anexpensive proposition. Consider, for example, a SCSI controller and its overloaded bus. To increase itsbandwidth, the SCSI controller (and likely all devices attached to it) would need to be replaced withfaster hardware. If the SCSI controller is a separate card, this would be a relatively straightforwardprocess, but if the SCSI controller is part of the system’s motherboard, it becomes much more difficultto justify the economics of such a change.3.1.5. In Summary. . .All system administrators should be aware of bandwidth, and how system configuration and usageimpacts available bandwidth. Unfortunately, it is not always apparent what is a bandwidth-relatedproblem and what is not. Sometimes, the problem is not the bus itself, but one of the componentsattached to the bus.