Local Area Networks, 3rd Edition David A. Stamper Part 2: Hardware Chapter 5 LAN Hardware

Chapter Preview Servers Backup devices Workstation hardware In this chapter you will study: Servers Backup devices Workstation hardware LAN adapters Printers Miscellaneous hardware

Server Platforms File Services File Servers Database Servers A file server allows users to share files. Only one copy of application software like word processing, spreadsheet, or database must reside on a file server. Individual clients share these applications. Database Servers The database server was developed to solve problems like passing an entire file over the medium. The most common example of a database server is the SQL server. Structured query language (SQL) is a standard database definition, access, and update language for relational databases.

Server Platforms (cont.) Print Services When a client shares a printer on the KAN, it can submit jobs to the printer at any time. The print job is collected on disk, and printing is deferred until the printer is available for printing a new job and the print job is the next one eligible to be printed.

Print Server Technology Client Print Server Application Server Spooler Client Spooler Print Monitor Router

Server Selection Considerations Server Disk Drives When choosing a server, you should carefully select the server’s disk subsystem. There are five factors that are critical when choosing a server’s disk subsystem: Storage Capacity Average Access Time Separation of Function Fault Tolerance Drive Interface

Server Selection Considerations (cont.) Server Memory In Intel-based servers, there are two classes of memory—Level 1/2 cache and standard random access memory (RAM) Processors and Processor Speed The processing power of the server is also a critical factor. It seldom makes sense to select a server that has fast disks and plenty of memory but a slow CPU. In general, the server ought to be one of the fastest—if not the fastest—computers on the network.

Server Selection Considerations (cont.) Processor Bus A variety of buses are available. The bus is the path over which data is transferred between the CPU, memory, and peripherals. Expansion and Power A server should have sufficient expansion capability and the power to use the expansion slots effectively. Network server capacity can be expanded by adding hardware to the existing server or by adding additional servers. Compatibility The server platform you choose must be compatible with the topology, MAC protocol, applications, and system software on the network.

IBM-Compatible System Buses Industry standard architecture (ISA) Enhanced industry standard architecture (EISA) Micro channel architecture (MCA) VESA local (VL-Bus) Video electronics standards association (VESA) Peripheral component interconnect (PCI) PC-Card (formerly PCMCIA)

Backup Devices Floppy Diskette Drives Removable Disk Drives The major disadvantages of this backup method is the low capacity and speed of the backup media. Removable Disk Drives Manual intervention is necessary for changing disk cartridges, whereas some tape backup system provide tapes with much higher storage capacity and with automatic tape changing. Hard-Disk Drives The arguments for and against this alternative are much the same as those for diskettes. The major difference is that the capacity of hard-disk drives is greater than that of diskettes.

Backup Devices (cont.) Optical Disk Drives Magnetic Tape Drives Optical disk drives are gaining popularity as input, output, and backup devices. The reasons for this are their decreasing costs and large storage capacity. Magnetic Tape Drives A magnetic tape drive is the usual choice for a backup device. Magnetic tapes are less expensive than the other options. They hold large volumes of data, are easy to use and store, and generally provide good performance.

Primary Backup Technologies Diskette backup Hard drive, fixed Hard drive, removable cartridge Tape backup, 4mm or 1/4 inch Tape backup, 8mm or VCR Tape backup, 9-track Optical drives Digital versatile disks (when available) 1.44 MB Multiple capacities 40 MB to over 1 G To 15 GB 160 MB 2.2 GB To 2.2 GB To 100 MB To 4 GB 10-14 GB 2.88 MB 60 MB 500 MB 15 GB 20 MB 150 MB 1.2 GB 70 GB (compressed)

Backup Functions Back up all files Differential backup Back up all files modified since a particular date Back up by directory Back up automatically by time or calendar Back up all but a list of files to be excluded Start backup from workstation or server Back up by interface to a database Back up using wildcard characters in file names Incremental backup Maintain index on tape and disk Maintain cross-reference of tape serial numbers and backup Back up manually Back up by list of files Back up by index Compress data Back up multiple volumes Generate reports

Workstations Diskless Workstations Workstation Memory and Speed A diskless workstation does not have any local disk drives. Instead, a diskless workstation has its boot logic in a read-only memory (ROM) chip located on the LAN adapter. Because diskless workstations have no disk drives, they are inherently less expensive than those with disks. Workstation Memory and Speed The speed of the workstation’s processor must be compatible with the type of work for which it is being used. Basically, it is the application, not the LAN, that determines the power of the workstations.

LAN Adapters If you have chosen an architecture, medium, and media access control protocol, you have narrowed the options for LAN adapters, also known as a network interface card (NIC). LAN adapters provide the connection between the medium and the bus of the workstation or server. LAN adapters are designed to support a specific protocol using a specific medium, although a few can support two or three different medium types.

Printers One major factor that affects the success of a LAN is printer support. Some LANs have restrictions regarding the distribution of printers and the number of printers that can be supported by one server. A printer driver is a software module that determines how to format data for proper printing on a specific type of printer. The printers you intend to use must be supported by the software drivers provided by the LAN operating system or printer vendor.

Hubs and Switches Some LAN architectures use wiring hubs to provide device interconnection. Hubs vary in the number of ports available. A very common configuration is 8 ports, with 12- and 16-port hubs as common alternatives. Hubs may be stand-alone or stackable.

Making Connections The objective of network connection—that is, connecting a computer to the LAN medium—is to provide a data path between the medium and the computer’s memory. The interface or connection to the medium is called the communications interface unit (CIU), and the interface or connection to the computer’s bus is called the bus interface unit (BIU).

Details of Node-to-Medium Connection LAN Node Node’s I/O Bus Bus interface Unit (BIU) Transceiver Communications Interface Unit (CIU) LAN Medium

Transceiver Located on a LAN Adapter Ethernet Controller Encoder/ Decoder Transceiver RAM Bus Interface Cable