Servers
Server computers are the lifeblood of any network. Servers provide the shared resources that network users crave, such as file storage, databases, e-mail, Web services, and so on. Choosing the equipment you use for your network’s servers is one of the key decisions you’ll make when you set up a network. In this section, I describe some of the various ways you can equip your network’s servers.
What’s important in a server
✦ Scalability: Scalability refers to the ability to increase the size and capacity of the server computer without unreasonable hassle. It is a major mistake to purchase a server computer that just meets your current needs because, you can rest assured, your needs will double within a year. If at all possible, equip your servers with far more disk space, RAM, and processor power than you currently need.
✦ Reliability: The old adage “you get what you pay for” applies especially well to server computers. Why spend $3,000 on a server computer when you can buy one with similar specifications at a discount electronics store for $1,000? One reason is reliability. When a client computer fails, only the person who uses that computer is affected. When a server fails, however, everyone on the network is affected. The less expensive computer is probably made of inferior components that are more likely to fail.
✦ Availability: This concept of availability is closely related to reliability. When a server computer fails, how long does it take to correct the problem and get the server up and running again? Server computers are designed so that their components can be easily diagnosed and replaced, thus minimizing the downtime that results when a component fails. In some servers, components are hot swappable, which means that certain components can be replaced without shutting down the server. Some servers are designed to be fault-tolerant so that they can continue to operate even if a major component fails. For more information about fault-tolerant computers, see the sidebar “Tolerant to a fault.”
✦ Service and support: Service and support are factors often overlooked when picking computers. If a component in a server computer fails, do you have someone on site qualified to repair the broken computer? If not, you should get an on-site maintenance contract for the computer. Don’t settle for a maintenance contract that requires you to take the computer in to a repair shop or, worse, mail it to a repair facility. You
can’t afford to be without your server that long.
Components of a server computer
✦ Motherboard: The motherboard is a single, large electronic circuit board to which all the other components of your computer are connected. More than any other component, the motherboard is the computer. All other components attach to the motherboard. The major components on the motherboard include the processor (or CPU), supporting circuitry called the chipset, memory, expansion slots, a standard IDE hard drive controller, and I/O ports for devices such as keyboards, mice, and printers. Some motherboards also include additional built-in features such as a graphic adapter, SCSI disk controller, or
a network interface.
✦ Processor: The processor, or CPU, is the brain of the computer. Although the processor isn’t the only component that affects overall system performance, it is the one that most people think of first when deciding what type of server to purchase. At the time of this writing, Intel had four processor models, summarized in Table 3-1. Two of them — the Pentium 4 and Celeron — should be used only for desktop or notebook computers. Server computers should have an Itanium 2 or a Xeon processor, or a comparable processor from one of Intel’s competitors, such as AMD. Each motherboard is designed to support a particular type of processor. CPUs come in two basic mounting styles: slot or socket. However, you can choose from several types of slots and sockets, so you have to make sure that the motherboard supports the specific slot or socket style used by the CPU. Some server motherboards have two or more
slots or sockets to hold two or more CPUs. The term clock speed refers to how fast the basic clock that drives the processor’s operation ticks. In theory, the faster the clock speed, the faster the processor. However, clock speed alone is reliable only for comparing processors within the same family. In fact, the Xeon is significantly faster than the Pentium 4 running at the same clock speed. That’s because the Xeon contains more advanced circuitry than the Pentium 4, so it’s able to accomplish more work than the Pentium 4 with each tick of the clock.
✦ Memory: Don’t scrimp on memory. People rarely complain about servers having too much memory. Many different types of memory are available, so you have to pick the right type of memory to match the memory supported by your motherboard. The total memory capacity of the server depends on the motherboard. Most new servers can support up to 12GB of memory.
✦ Hard drives: Most desktop computers use inexpensive hard drives called IDE drives. These drives are adequate for individual users, but because performance is more important for servers, another type of drive known as SCSI is usually used instead. For the best performance, use the SCSI drives along with a high-performance SCSI controller card.
✦ Network connection: The network connection is one of the most important parts of any server. Many servers have network adapters built into the motherboard. If your server isn’t equipped as such, you’ll need to add a separate network adapter card. See the section “Network Adapters,” later in this chapter, for more information.
✦ Video: Fancy graphics aren’t that important for a server computer. You can equip your servers with inexpensive generic video cards and monitors without affecting network performance. (This is one of the few areas where it’s acceptable to cut costs on a server.)
✦ Power supply: Because a server usually has more devices than a typical desktop computer, it requires a larger power supply (300 watts is typical). If the server houses a large number of hard drives, it may require an even larger power supply.
Server form factors
The term form factor refers to the size, shape, and packaging of a hardware device. Server computers typically come in one of three form factors:
✦ Tower case: Most servers are housed in a traditional tower case, similar to the tower cases used for desktop computers. A typical server tower case is 18 inches high, 20 inches deep, and 9 inches wide and has room inside for a motherboard, five or more hard drives, and other components. Tower cases also come with built-in power supplies. Some server cases include advanced features specially designed for servers, such as redundant power supplies (so both servers can continue operating if one of the power supplies fails), hot-swappable fans, and hot-swappable disk drive bays. (Hot-swappable components can be replaced without powering down the server.)
✦ Rack mount: If you only need a few servers, tower cases are fine. You can just place the servers next to each other on a table or in a cabinet that’s specially designed to hold servers. If you need more than a few servers, though, space can quickly become an issue. For example, what if your departmental network requires a bank of ten file servers? You’d need a pretty long table. Rack-mount servers are designed to save space when you need more than a few servers in a confined area. A rack-mount server is housed in a small chassis that’s designed to fit into a standard 19-inch equipment rack. The rack allows you to vertically stack servers in order to save space. Because of their small size, rack-mount servers are not as expandable as tower-style servers. A typical system includes built-in video and network connections, room for three hard drives, two empty expansion slots for additional adapters, and a SCSI port to connect additional external hard drives.
✦ Blade servers: Blade servers are designed to save even more space than rack-mount servers. A blade server is a server on a single card that can be mounted alongside other blade servers in a blade chassis, which itself fits into a standard 19-inch equipment rack. A typical blade chassis holds six or more servers, depending on the manufacturer. One of the key benefits of blade servers is that you don’t need a separate power supply for each server. Instead, the blade enclosure provides power for all its blade servers. Some blade server systems provide rack-mounted power supplies that can serve several blade enclosures mounted in a single rack. In addition, the blade enclosure provides KVM switching so that you don’t have to use a separate KVM switch. You can control any of the servers in a blade server network from a single keyboard, monitor, and mouse. One of the biggest benefits of blade servers is that they drastically cut down the amount of cable clutter. With rack-mount servers, each server requires its own power cable, keyboard cable, video cable, mouse cable, and network cables. With blade servers, a single set of cables can service all the servers in a blade enclosure.
Server computers are the lifeblood of any network. Servers provide the shared resources that network users crave, such as file storage, databases, e-mail, Web services, and so on. Choosing the equipment you use for your network’s servers is one of the key decisions you’ll make when you set up a network. In this section, I describe some of the various ways you can equip your network’s servers.
What’s important in a server
✦ Scalability: Scalability refers to the ability to increase the size and capacity of the server computer without unreasonable hassle. It is a major mistake to purchase a server computer that just meets your current needs because, you can rest assured, your needs will double within a year. If at all possible, equip your servers with far more disk space, RAM, and processor power than you currently need.
✦ Reliability: The old adage “you get what you pay for” applies especially well to server computers. Why spend $3,000 on a server computer when you can buy one with similar specifications at a discount electronics store for $1,000? One reason is reliability. When a client computer fails, only the person who uses that computer is affected. When a server fails, however, everyone on the network is affected. The less expensive computer is probably made of inferior components that are more likely to fail.
✦ Availability: This concept of availability is closely related to reliability. When a server computer fails, how long does it take to correct the problem and get the server up and running again? Server computers are designed so that their components can be easily diagnosed and replaced, thus minimizing the downtime that results when a component fails. In some servers, components are hot swappable, which means that certain components can be replaced without shutting down the server. Some servers are designed to be fault-tolerant so that they can continue to operate even if a major component fails. For more information about fault-tolerant computers, see the sidebar “Tolerant to a fault.”
✦ Service and support: Service and support are factors often overlooked when picking computers. If a component in a server computer fails, do you have someone on site qualified to repair the broken computer? If not, you should get an on-site maintenance contract for the computer. Don’t settle for a maintenance contract that requires you to take the computer in to a repair shop or, worse, mail it to a repair facility. You
can’t afford to be without your server that long.
Components of a server computer
✦ Motherboard: The motherboard is a single, large electronic circuit board to which all the other components of your computer are connected. More than any other component, the motherboard is the computer. All other components attach to the motherboard. The major components on the motherboard include the processor (or CPU), supporting circuitry called the chipset, memory, expansion slots, a standard IDE hard drive controller, and I/O ports for devices such as keyboards, mice, and printers. Some motherboards also include additional built-in features such as a graphic adapter, SCSI disk controller, or
a network interface.
✦ Processor: The processor, or CPU, is the brain of the computer. Although the processor isn’t the only component that affects overall system performance, it is the one that most people think of first when deciding what type of server to purchase. At the time of this writing, Intel had four processor models, summarized in Table 3-1. Two of them — the Pentium 4 and Celeron — should be used only for desktop or notebook computers. Server computers should have an Itanium 2 or a Xeon processor, or a comparable processor from one of Intel’s competitors, such as AMD. Each motherboard is designed to support a particular type of processor. CPUs come in two basic mounting styles: slot or socket. However, you can choose from several types of slots and sockets, so you have to make sure that the motherboard supports the specific slot or socket style used by the CPU. Some server motherboards have two or more
slots or sockets to hold two or more CPUs. The term clock speed refers to how fast the basic clock that drives the processor’s operation ticks. In theory, the faster the clock speed, the faster the processor. However, clock speed alone is reliable only for comparing processors within the same family. In fact, the Xeon is significantly faster than the Pentium 4 running at the same clock speed. That’s because the Xeon contains more advanced circuitry than the Pentium 4, so it’s able to accomplish more work than the Pentium 4 with each tick of the clock.
✦ Memory: Don’t scrimp on memory. People rarely complain about servers having too much memory. Many different types of memory are available, so you have to pick the right type of memory to match the memory supported by your motherboard. The total memory capacity of the server depends on the motherboard. Most new servers can support up to 12GB of memory.
✦ Hard drives: Most desktop computers use inexpensive hard drives called IDE drives. These drives are adequate for individual users, but because performance is more important for servers, another type of drive known as SCSI is usually used instead. For the best performance, use the SCSI drives along with a high-performance SCSI controller card.
✦ Network connection: The network connection is one of the most important parts of any server. Many servers have network adapters built into the motherboard. If your server isn’t equipped as such, you’ll need to add a separate network adapter card. See the section “Network Adapters,” later in this chapter, for more information.
✦ Video: Fancy graphics aren’t that important for a server computer. You can equip your servers with inexpensive generic video cards and monitors without affecting network performance. (This is one of the few areas where it’s acceptable to cut costs on a server.)
✦ Power supply: Because a server usually has more devices than a typical desktop computer, it requires a larger power supply (300 watts is typical). If the server houses a large number of hard drives, it may require an even larger power supply.
Server form factors
The term form factor refers to the size, shape, and packaging of a hardware device. Server computers typically come in one of three form factors:
✦ Tower case: Most servers are housed in a traditional tower case, similar to the tower cases used for desktop computers. A typical server tower case is 18 inches high, 20 inches deep, and 9 inches wide and has room inside for a motherboard, five or more hard drives, and other components. Tower cases also come with built-in power supplies. Some server cases include advanced features specially designed for servers, such as redundant power supplies (so both servers can continue operating if one of the power supplies fails), hot-swappable fans, and hot-swappable disk drive bays. (Hot-swappable components can be replaced without powering down the server.)
✦ Rack mount: If you only need a few servers, tower cases are fine. You can just place the servers next to each other on a table or in a cabinet that’s specially designed to hold servers. If you need more than a few servers, though, space can quickly become an issue. For example, what if your departmental network requires a bank of ten file servers? You’d need a pretty long table. Rack-mount servers are designed to save space when you need more than a few servers in a confined area. A rack-mount server is housed in a small chassis that’s designed to fit into a standard 19-inch equipment rack. The rack allows you to vertically stack servers in order to save space. Because of their small size, rack-mount servers are not as expandable as tower-style servers. A typical system includes built-in video and network connections, room for three hard drives, two empty expansion slots for additional adapters, and a SCSI port to connect additional external hard drives.
✦ Blade servers: Blade servers are designed to save even more space than rack-mount servers. A blade server is a server on a single card that can be mounted alongside other blade servers in a blade chassis, which itself fits into a standard 19-inch equipment rack. A typical blade chassis holds six or more servers, depending on the manufacturer. One of the key benefits of blade servers is that you don’t need a separate power supply for each server. Instead, the blade enclosure provides power for all its blade servers. Some blade server systems provide rack-mounted power supplies that can serve several blade enclosures mounted in a single rack. In addition, the blade enclosure provides KVM switching so that you don’t have to use a separate KVM switch. You can control any of the servers in a blade server network from a single keyboard, monitor, and mouse. One of the biggest benefits of blade servers is that they drastically cut down the amount of cable clutter. With rack-mount servers, each server requires its own power cable, keyboard cable, video cable, mouse cable, and network cables. With blade servers, a single set of cables can service all the servers in a blade enclosure.
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