Web Server Administration

1
Web Server Administration

• Chapter 2
• Preparing For Server Installation

2
Overview

• Identify server categories
• Evaluate server components
• Plan for system disasters and reduce their
  effects
• Evaluate network components
• Set up IP addressing

3
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

4
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

5
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

6
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

7
Evaluating Server Components-UltraSPARC
Processors

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

8
Evaluating Server Components-UltraSPARC
Processors
9
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

10
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

11
Evaluating Server Components-Selecting a NIC
12
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

13
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

14
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

15
Disk Redundancy through RAID

• RAID 0
• Has technique call disk stripping
• Data is spread over a number of disks
• Fastest eliminates disk failures
• RAID 2
• Error correcting codes for drives that do not
  have built-in error detection.
• SCSI come with error detection If any one of the
  drives fails, data can be recovered from the
  remaining drives

16
Disk Redundancy through RAID

• RAID 3
• Strips data across the disk drives at the byte
  level.
• Information needed to rebuild data is stored on
  one drive
• RAID 4
• Similar to 3
• Reads are as fast as RAID 0, but writes are slow
  because extra information must be stored for
  rebuilding purposes.

17
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

18
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

19
Achieving High Availability with Multiple Servers

• Many computers act as one
• Can have tens of thousands of computers
• IBM uses computers in a cluster that serve
  different purposes
• Microsofts approach is to distribute the
  computing load among distinct servers

20
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

21
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

22
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

23
Setting Up IP Addressing

• IP addresses are divided into the network portion
  and the host portion
• The subnet mask distinguishes the two portions

24
Common IP Classes
25
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

26
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