Each device has its own problems, but the bandwidth available to network interfaces and the bandwidth available to disks are the two primary causes of bottlenecks in I/O performance.
Network I/O problems:
Network overload:
The amount of data transported over the network is larger than the network's capacity, resulting in slow execution of every network related task for all users. They can be solved by cleaning up the network (which mainly involves disabling protocols and services that you don't need) or by reconfiguring the network (for example use of subnets, replacing hubs with switches, upgrading interfaces and equipment).
Network integrity problems:
Occurs when data is transferred incorrectly. Solving this kind of problem can only be done by isolating the faulty element and replacing it.
Disk I/O problems:
per-process transfer rate too low:
Read or write speed for a single process is not sufficient.
aggregate transfer rate too low:
The maximum total bandwidth that the system can provide to all programs that run is not enough.
This kind of problem is more difficult to detect, and usually takes extra hardware in order to re-divide data streams over buses, controllers and disks, if overloaded hardware is cause of the problem. One solution to solve this is a RAID array configuration optimized for input and output actions. This way, you get to keep the same hardware. An upgrade to faster buses, controlers and disks is usually the other option.
If overload is not the cause, maybe your hardware is gradually failing, or not well connected to the system. Check contacts, connectors and plugs to start with.
4.3.5.5. Users
Users can be divided in several classes, depending on their behavior with resource usage:
Users who run a (large) number of small jobs: you, the beginning Linux user, for instance.
Users who run relatively few but large jobs: users running simulations, calculations, emulators or other programs that eat a lot of memory, and usually these users have accompanying large data files.
Users who run few jobs but use a lot of CPU time (developers and the like).
You can see that system requirements may vary for each class of users, and that it can be hard to satisfy everyone. If you are on a multi-user system, it is useful (and fun) to find out habits of other users and the system, in order to get the most out of it for your specific purposes.
4.3.5.6. Graphical tools
For the graphical environment, there are a whole bunch of monitoring tools available. Below is a screen shot of the Gnome System Monitor, which has features for displaying and searching process information, and monitoring system resources:
Figure 4-3. Gnome System Monitor
There are also a couple of handy icons you can install in the task bar, such as a disk, memory and load monitor. xload is another small X application for monitoring system load. Find your favorite!
4.3.5.7. Interrupting your processes
As a non-privileged user, you can only influence your own processes. We already saw how you can display processes and filter out processes that belong to a particular user, and what possible restrictions can occur. When you see that one of your processes is eating too much of the system's resources, there are two things that you can do:
Make the process use less resources without interrupting it;
Stop the process altogether.
In the case that you want the process to continue to run, but you also want to give the other processes on
