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Web Server Administration

Chapter 2Preparing For Server

Installation

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Overview

Identify server categories Evaluate server components Plan for system disasters and

reduce their effects Evaluate network components Set up IP addressing

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Identifying Server Categories-File Servers File servers emphasize sending and

receiving files A fast disk subsystem is more important

than the processor type File servers are useful in a Web

environment when you have a large number of static HTML pages

File servers are also appropriate for an FTP server

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Identifying Server Categories-Application Servers Server applications can process requests

from many users at a time Requires extensive processing power A DBMS is a typical example Exchange Server does more than send e-

mail messages Its complexity puts more burden on the

processor Servers may also combine the need for

fast processors and fast disk subsystems

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Evaluating Server Components-Intel Processors

Most common Intel processor is based on the 386

32-bit processors Data is processed 32 bits at a time

Uses CISC (Complex Instruction Set Computer) architecture

Linux files often end in i386 These files can be used with all current PCs

with the exception of the ones with the Itanium processor

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Evaluating Server Components-Intel Processors

Comparing processor speeds across processor versions can be deceiving Each newer processor version is much more

efficient at processing data at a given speed

Processor RAM L2 cache Bus speed

Pentium 4 Dual Channel RDRAM; PC 133 SDRAM; DDR 200/266 SDRAM

512 K >400 MHz

Pentium III Xeon

Dual Channel DDR; SDRAM

up to 2 MB up to 400 MHz

Celeron SDRAM 128 K or 256 K

up to 100 MHz

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Evaluating Server Components-UltraSPARC Processors

Manufactured by Sun Only used in computers from Sun 64-bit processors Uses RISC (Reduced Instruction Set

Computer) architecture

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Evaluating Server Components-UltraSPARC Processors

Processor Relative speed Maximum L2 cache

Maximum number of processors

Bus speed

UltraSPARC III Cu Fastest 8 MB over 1000 150 MHz

UltraSPARC II About 50% of III Cu 8 MB 64 66 MHz

UltraSPARC IIi About 50% of III Cu 2 MB 4 66 MHz

UltraSPARC IIe About 50% of III Cu 256 KB 4 66 MHz

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Evaluating Server Components-Using Multiple Processors

BEA WebLogic can assign multiple server applications to a single processor in a multi-processor environment

Processing a single application, such as a DBMS, spread over multiple processors is more common

Applications have to be designed to take advantage of multiple processors

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Evaluating Server Components-Selecting a Hard Drive Interface

IDE drives are less capable than SCSI Limited ability to add drives

SCSI can support many drives Ultra3, also known as Ultra160, is

one of the most common interfaces used in servers Manufactured by Adaptec

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Evaluating Server Components-Selecting a NIC

NIC Type Speed Media Use

Standard Ethernet

10 Mbps Twisted pair (sometimes fiber)

Workstations

Fast Ethernet

100 Mbps Twisted pair (sometimes fiber)

Workstations and

small to medium

servers

Gigabit Ethernet

1,000 Mbps Fiber (sometimes twisted pair)

High-end servers

10-Gigabit Ethernet

10,000 Mbps Fiber Backbone connections

ATM 25 Mbps – 622+ Mbps

Fiber Workstations and

servers (rare)

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Disaster Planning

Helps you avoid problems with hardware and software

A challenge to balance costs with benefits

In a server, the objective is fault tolerance The ability of a system to keep running

even when a component fails

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Disaster Assessment and Recovery Determine what can go wrong,

what effects it will have on the organization, and what it will take to fix

Hardware – determine what will happen if each component fails How to replace failed hardware How to restore software (if applicable) Who will diagnose hardware problems

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Disaster Assessment and Recovery Software disasters are more complex

than hardware disasters Could be a combination of application

software and the operating system You may be directed to install software

that may not work correctly Document installation and problems in

detail Make sure that support is available

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System Redundancy Often servers and switches have multiple

power supplies so if one fails, the other(s) can take over

In case the devices do not have redundancy built in, try to have as much spare hardware on hand as appropriate for the number of devices, reliability, and cost Also useful are warrantees that allow for

replacement within 24 hours

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Disk Redundancy through RAID RAID 1

Data is duplicated across two drives Also called mirroring If there are two adapters, it is called

duplexing RAID 5 (most common)

Distributes data across a minimum of 3 drives

If any one of the drives fails, data can be recovered from the remaining drives

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Achieving High Availability with Multiple Servers

Many computers act as one Can have ten’s of thousands of

computers IBM uses computers in a cluster

that serve different purposes Microsoft’s approach is to distribute

the computing load among distinct servers

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Setting Up Backup Systems You should maintain a series of backups

so you can restore data from a specific date

Types of backup methods Full – all data is backed up Differential – backs up all files that are new or

changed since last full backup Incremental – backs up all files that are new

or changed since the last incremental backup

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Backup Considerations Back up complete operating system

On Windows systems, you have to make sure that the Registry is backed up

Back up special application files DBMSs and Exchange keep files open, which

cannot be backed up without special backup software modules

Back up data files Easy and straightforward unless user has

files open

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Evaluating Network Components Hubs should be avoided in a server

environment Increased traffic slows communication

Switches can come close to the appearance of a dedicated circuit between servers

Routers connect one network to another

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Setting Up IP Addressing IP addresses are

divided into the network portion and the host portion

The subnet mask distinguishes the two portions

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Common IP Classes

Class First number Subnet mask Number of networks

Number of hosts

Class A 1 – 127 255.0.0.0 126 >16,000,000

Class B 128 – 191 255.255.0.0 > 16,000 >65,000

Class C 192 – 223 255.255.255.0 > 2,000,000 254

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Network Address Translation(NAT) NAT allows an IP address from one

network to be translated into another address on an internal network

You can also use NAT to translate a single IP address valid on the Internet into multiple internal addresses Useful if your ISP gives you a single IP

address, yet you have multiple servers and users on the internal network

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Summary File servers and application servers are

the two basic types of servers Various families of processors are

available from Intel, Sun, and others There are many techniques for

minimizing loss due to hardware and software failures

Routers and switches allow servers to communicate

IP addresses are divided into the network and host portions