Microsoft Office 2000/Visual Basic Programmer's Guide

Minimizing Network Bottlenecks

Finally, investigate bottlenecks occurring on your LAN that are due to hardware. You may want to try the following:

• Segment the LAN into subnets   Typically, a server has only one network interface card (NIC) with many nodes connected to it. To reduce this bottleneck, add multiple NICs to the server and spread the nodes across those segments. This is probably the cheapest and biggest performance improvement because it substantially reduces collisions on the wire and gives each station a larger slice of bandwidth to communicate with the server.
  
  
• Add a better NIC to the server   Practically all Pentium systems now come with slots for the Peripheral Component Interconnect (PCI) bus. By using PCI NICs you can experience significantly faster throughput while keeping the central processing unit (CPU) usage lower. Also, many PCI NICs offer a multiported design, thus allowing you to do multiple segments from one PCI NIC. An example of this is a server with two PCI slots that uses two four-port PCI NICs. This creates 8 segments that go to 36 nodes to reduce collisions on the wire and increase the bandwidth that is available to each node when it is communicating with the server. This would allow you to focus on performance issues that are software-related instead of hardware-related.

  Another option with PCI NICs is the 100 MB Ethernet standard. Although the 100 MB hubs required to accompany the 100 MB NICs are expensive, they do provide an alternative to finding workarounds for performance issues over the wire, and they can use existing cabling.

• Add faster disk drives and host adapters to the server   Again, moving to PCI- or Extended Industry Standard Architecture (EISA) -based host adapters can have a significant impact on performance. To eliminate this bottleneck, one approach is to configure the server to use an EISA SCSI RAID controller using eight 1-GB Small Computer System Interface (SCSI) drives. This increases performance because the EISA card reduces CPU processing by handling some processing itself, and because the Redundant Array of Inexpensive Disks (RAID) configuration allows reads and writes to be spread across the eight disk drives, thus reducing contention issues when multiple users try to access a drive. This is probably the most expensive solution, but it makes a big performance improvement over a one-ISA-card, one-disk solution.