Web Server Administration

Web Server Administration

Chapter 2

Preparing For Server Installation

Overview

■ Identify server categories

■ Evaluate server components

■ Plan for system disasters and reduce their effects

■ Evaluate network components

■ Set up IP addressing

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

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

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

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 Rambus DRAM; 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 – Synchronous Dynamic Random Access Memory

128 K or 256 K

up to 100

MHz

Evaluating Server Components- UltraSPARC Processors

■ Manufactured by Sun

■ Only used in computers from Sun

■ 64-bit processors

■ Uses RISC (Reduced Instruction Set

Computer) architecture

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

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

Using Multiple Processors – Amdahl’s Law

■ SMP – Symmetric Multiprocessing

■ Allows server to divide processes and assign them to available processors.

■ Amdahl’s Law

■ The speedup of a program using multiple

processors in parallel computing is limited

by the time needed for the sequential part

of a program

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

Selecting a Hard Drive

■ Mean Time Between Failure (MTBF)

■ Capacity (GB)

■ Data Transfer Rate

■ Hard drive to buffer

■ Buffer to Adapter

■ Buffer size

■ Average Seek Time

■ Rotational Speed (RPM)

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

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

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

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

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

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

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

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

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

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

Setting Up IP Addressing

■

IP addresses are divided into the

network portion and the host portion

■

The subnet mask

distinguishes the

two portions

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

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

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