Chapter 9 Introduction to the Server
375
backplane
a simple mother-
board designed with
minimal compo-
nents. It typically
serves as the inter-
face of all the major
components.
hot swapping
the process of
removing compo-
nents without
shutting down the
system.
Power Supply
The power supply converts standard 120-volt or 240-volt AC power into lower
DC voltage levels that can be used by the motherboard and other devices inside
the computer case. A typical power supply provides an assortment of output plugs.
The plug style matches the intended piece of equipment. For example, a standard
ATA drive uses a Molex plug, which supplies 5 volts DC and 12 volts DC to the
ATA drive. An ATX-style motherboard plug supplies 3.3 volts, 5 volts, and 12 volts
as well as a ground connection to the motherboard. It is also designed to plug into
the motherboard correctly. Older style connections could be incorrectly plugged
into the motherboard if you did not pay attention to the color-coding.
Entry-level servers are typically equipped with two power supplies,
Figure 9-5. The two power supplies balance the load. If one power supply fails,
the other power supply carries the full load. Some servers are designed with
“hot-swappable” power supplies, which permit the defective power supply to be
changed while the server is running.
To prevent the loss of data, most server manufacturers recommend disconnecting
the server from the network while replacing hot-swappable power supplies.
Motherboard
Servers generally use a backplane. A backplane is a simple motherboard
designed with minimal components. It typically serves as the interface of all
the major components. It is designed to allow major components to be added or
removed without powering down the system. Removing components without
shutting down the system is call hot swapping.
Figure 9-6 shows the general backplane layout of the HP ProLiant DL740 server
with and without the added modules. An I/O board attaches to the backplane. It
contains six PCI hot-swappable slots. The processor boards each contain 4 CPUs, for
a total of 8 CPUs. Each memory module in the system is hot-swappable and contains
8 DIMMS. The HP ProLiant DL740 can contain up to 40 GB of RAM. The multiple
CPUs and vast amount of RAM are required to provide the many different services to
Figure 9-5.
Back view of the
ProLiant ML350.
This system comes
with two power
supplies that evenly
distribute power
throughout the
system. When one
power supply fails,
the other carries the
full load. (Hewlett-
Packard Company)
Power supplies