Chapter 3. Bandwidth and Processing Power

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3.1.4. Potential Bandwidth related Solutions

Fortunately, bandwidth related problems can be addressed. In fact, there are several approaches you

can take:

Spread the load

Reduce the load

Increase the capacity

The following sections explore each approach in more detail.

3.1.4.1. Spread the Load

Another approach is to more evenly distribute the bus activity. In other words, if one bus is overloaded

and another is idle, perhaps the situation would be improved by moving some of the load to the idle

bus.

As a system administrator, this is the first approach you should consider, as often there are additional

buses already present in your system. For example, most PCs include at least two IDE channels (which

is just another name for a bus). If you have two IDE disk drives and two IDE channels, why should

both drives be on the same channel?

Even if your system configuration does not include additional buses, spreading the load might still be

a reasonable approach. The hardware expenditures to do so would be less expensive than replacing an

existing bus with higher capacity hardware.

3.1.4.2. Reduce the Load

At 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 to de 

termine 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 small tem 

porary file is the recipient of heavy read/write I/O. If that temporary file was created on a networked

file server, a great deal of network traffic could be eliminated by working with the file locally.

3.1.4.3. Increase the Capacity

The obvious solution to insufficient bandwidth is to increase it somehow. However, this is usually

an expensive proposition. Consider, for example, a SCSI controller and its overloaded bus. In order

to increase its bandwidth, the SCSI controller (and likely all devices attached to it) would need to

be replaced with faster hardware. If the SCSI controller is a separate card, this would be a relatively

straightforward process, but if the SCSI controller is part of the system's motherboard, it becomes

much more difficult to 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 usage

impacts available bandwidth. Unfortunately, it is not always apparent what is a bandwidth related

problem and what is not. Sometimes, the problem is not the bus itself, but one of the components

attached to the bus.