The Five Most Common Network Bottlenecks

Direct from the home office in sunny Fresno, California, here are the ten-oops, five-most common network bottlenecks, in no particular order.

The hardware inside your servers

Your servers should be powerful computers capable of handling all the work your network will throw at them. Don't cut corners by using a bottom-of-the-line computer that you bought at a discount computer store.

The following list describes the four most important components of your server hardware:

• Processor: Your server should have a powerful processor. Any processor that's available in an $800 computer from a low-cost general appliance store is generally not a processor that you want to see in your file server. In other words, avoid processors designed for consumer-grade home computers.

• Memory: You can't have too much memory. Memory is cheap, so don't skimp. Don't even think about running a server with fewer than 2GB of RAM.

• Disk: Don't mess around with inexpensive IDE hard drives. To have a respectable system, you should have nothing but SCSI drives.

• Network card: A $9.95 network card may be fine for your home network, but don't use one in a file server that supports 100 users and expect to be happy with the server's performance. Remember that the server computer uses the network more often than any clients do. Equip your servers with good network cards.

The server's configuration options

All network operating systems have options that you can configure. Some of these options can make the difference between a pokey network and a zippy network. Unfortunately, no hard-and-fast rules exist for setting these options. Otherwise, you wouldn't have options.

The following important tuning options are available for most servers:

• Virtual memory options: Virtual memory refers to disk paging files that the server uses when it doesn't have enough real memory to do its work. Few servers ever have enough real memory, so virtual memory is always an important server feature. You can specify the size and location of the virtual memory paging files.

  Tip 

  For the best performance, provide at least 1 ½ times the amount of real memory. For example, if you have 4GB of real memory, allocate at least 6GB of virtual memory. If necessary, you can increase this size later.

• Disk striping: Use the disk defragmenter to optimize the data storage on your server's disks.

  Tip 

  If the server has more than one hard drive, you can increase performance by creating striped volumes, which allow disk I/O operations to run concurrently on each of the drives in the stripe set.

• Network protocols: Make sure that your network protocols are configured correctly and remove any protocols that aren't necessary.

• Free disk space on the server: Servers like to have plenty of breathing room on their disks.

  Warning 

  If the amount of free disk space on your server drops precipitously low, the server chokes up and slows to a crawl. Make sure that your server has plenty of space-a few gigabytes of unused disk space provides a healthy buffer.

Servers that do too much

One common source of network performance problems is a server overloaded with too many duties. Just because a modern network operating system comes equipped with dozens of different types of services doesn't mean that you should enable and use them all on a single server. If a single server is bogged down because of too much work, add a second server to relieve the first server of some of its chores. Remember the old saying: "Many hands make light work."

For example, if your network needs more disk space, consider adding a second file server rather than adding another drive to the server that already has four nearly full drives. Better yet, purchase a file server appliance dedicated to the task of serving files.

As a side benefit, your network will be easier to administer and more reliable if you place separate functions on separate servers. For example, if a single server doubles as a file server and a mail server, you lose both services if you have to take down the server to perform an upgrade or repair a failed component. However, if you have separate file and mail server computers, only one of the services is interrupted if you have to take down one of the servers.

The network infrastructure

The infrastructure consists of the cables and any switches, hubs, routers, and other components that sit between your clients and your servers.

REMEMBER 

The following network infrastructure items can slow down your network:

• Hubs: Because switches are inexpensive now, you can affordably solve many performance problems by replacing old, outdated hubs with switches. Using switches rather than hubs reduces the overall load on your network.

• Segment sizes: Keep the number of computers and other devices on each network segment to a reasonable number. About 20 devices is usually the right number. (Note that if you replace your hubs with switches, you instantly cut the size of each segment because each port on a switch constitutes a separate segment.)

• The network's speed: If you have an older network, you may discover that many-if not all-of your users are still working at 10 Mbps. Upgrading to 100 Mbps speeds up the network dramatically. Upgrading to 1 Gbps speeds it up even more.

• The backbone speed: If your network uses a backbone to connect segments, consider upgrading the backbone to 1 Gbps.

Tip 

The hardest part about improving the performance of a network is determining where the bottlenecks are. With sophisticated test equipment and years of experience, network gurus can make good educated guesses. Without the equipment and experience, you can still make good uneducated guesses.

Malfunctioning components

Sometimes a malfunctioning network card or other component slows down the network. For example, a switch may malfunction intermittently, occasionally letting packets through but dropping enough of them to slow down the network. After you identify the faulty component, replacing it restores the network to its original speed.