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The electricity the file server gets from the wall outlet may, from time to time, vary considerably in voltage (resulting in sags and spikes). To make your file server as reliable as possible, you should install an uninterruptable power supply (UPS) between the electric power source and your server. The UPS not only provides electricity in case of a power failure, but also conditions the line to protect the server from voltage fluctuations. In general, you want to do whatever you can to make your network reliable, including placing the server away from public access areas. Evaluating the File Server Hard Disk The hard disk drives are the most important components of a file server. The hard disks are where the people who use the LAN store their files. To a large extent, the reliability, access speed, and capacity of a servers hard disks determine whether people will be happy with the LAN and will be able to use it productively. The most common bottleneck in the average LAN is disk I/O time at the file server. And the most common complaint voiced by people on the average LAN is that the file server has run out of free disk space. Make sure that your file servers disk drives and hard disk controller are high-performance components, and that you always have plenty of free disk space on your servers drives. Evaluating the File Server CPU The file server CPU tells the hard disk drives what to store and retrieve. The CPU is the next most important file server component after the hard disks. Unless your LAN will have only a few users and will never grow, a file server with a fast Pentium, Pentium Pro, or Pentium II CPU and plenty of RAM is a wise investment. The next section discusses server RAM. The CPU chip in a computer executes the instructions given to it by the software you run. If you run an application, that application runs more quickly if the CPU is fast. Likewise, if you run a network operating system, that NOS runs more quickly if the CPU is fast. Some NOSes absolutely require certain types of CPU chips. NetWare version 2, for example, required at least a 286 CPU. NetWare versions 3 and 4 require at least a 386. IBM LAN Server version 2 and Microsoft LAN Manager version 2 require that OS/2 1.3 be running on the server computer; OS/2 1.3 requires an 80286 or later CPU. LAN Server 3.0 requires that the file server use OS/2 2.x, which runs only on 386 or later CPUs. Microsoft Windows NT Advanced Server 3.51 requires a 386DX25 or later CPU and 16M of RAM. These are, of course, the absolute minimum CPU requirements. Exceeding them is a practice that is highly recommended, for any of these products. Evaluating Server RAM The network operating system loads into the computers RAM, just like any other application. You need to have enough RAM in the computer for the NOS to load and run properly. On a peer LAN, the recommended amount of RAM would be whatever it takes to run your applications, whereas on a client/server LAN, you might install 32M, 64M, or more in your file server. Windows 95 in a peer-to-peer environment should have a minimum of 16M of RAM. Windows NT should have more. The proper amount of RAM for a server-based LAN operating system like NetWare is calculated using a formula that accounts for the software you will be running and the capacity and configuration of your disk drives. Be sure to follow the operating system manufacturers RAM recommendations carefully, or severe performance problems may result. You can realize significant performance gains in a NetWare server with a faster CPU and extra RAM because of a process called file caching. If the server has sufficient memory installed, it can remember those portions of the hard disk that it has accessed previously. When the next user asks for the same file represented by those portions of the hard disk, the server can send it to the next user without having to actually access the hard disk. Because the file server is able to avoid waiting for the hard disk to rotate into position, the server can do its job more quickly. The NOS merely needs to look in the computers RAM for the file data that a workstation has requested. Thus, you can be assured that any extra memory installed in your server will be put to beneficial use. Note that the NOSs caching of file data is distinct from (and in addition to) any caching that might occur due to the hard disk or hard disk controller card having on-board memory. Evaluating the Network Adapter Card The servers network adapter card is its link to all the workstations on the LAN. All file requests and other network communications enter and leave the server through the network adapter. As you can imagine, the network adapter in a server is a very busy component. All the network adapters on the LAN use Ethernet, Token Ring, ARCnet, or some other low-level protocol. You can find network adapters for each of these protocols, however, that perform better than others. A network adapter may be faster at processing messages because it has a large amount of on-board memory (RAM), because it contains its own microprocessor, or perhaps because the adapter uses a 16-bit or a 32-2-bit slot instead of an 8-bit slot and thus can transfer re da to and from the CPU at one time. 32-bit slots in server computers could be EISA, VLB, or PCI. PCI is currently the most commonly found 32-bit bus type in the Pentium class machine. A faster, more capable network adapter is an ideal candidate for installation in a file server, but be sure to check its compatibility with the network adapters installed in your workstations. Evaluating the Servers Power Supply In a file server, the power supply is an important but often overlooked item. Power supply failures and malfunctions can cause problems elsewhere in the computer that are difficult to diagnose. Your file server may display a message indicating that a RAM chip has failed, and then stop; the cause of the problem may indeed be a failed RAM chip, or the problem may be in the power supply. The fan(s) in the power supply sometimes stop working or become obstructed with dust and dirt. The computer overheats and fails completely or acts strangely. Cleaning the fan(s)after unplugging the computer from the wall outlet, of courseshould be a part of the regular maintenance of your file server.
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