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. Server Categories • What do you use the server for? • File Server • High-speed disk drivers • Application Server • High-speed processors • Depending on the server type we choose our hardware and software

4. Identifying Server Categories-File Servers • File servers emphasize on 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

5. Identifying Server Categories-Application Servers • Application Servers can process requests from many users at a time • Require extensive processing power • A DBMS is a typical example • Many contain dynamic HTML and scripting • Many email servers are considered as Application Servers • 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

6. 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 Pentium 4 with Clock speed: 3.4 GHz Number of transistors: 55 million

7. 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 Number of transistors? http://www.raptureready.com/time/rap31d.html

8. Evaluating Server Components-UltraSPARC Processors • Manufactured by Sun • Only used in computers from Sun • 64-bit processors • Uses RISC (Reduced Instruction Set Computer) architecture • More efficient than CISC

9. Evaluating Server Components-UltraSPARC Processors

10. 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

11. 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

12. Selecting a Hard Drive • Reliability • MTBF (Mean Time Between Failure) • Capacity • Data Transfer Rate • Buffer to HD / HD to buffer • Average Seek Time • Rotational Speed • How fast the disk spins (7 Krps) • Access Time • How long to retrieve the information. Includes the seek time

13. Evaluating Server Components-Selecting I/O Ports • Video • PCI • External and can be connected to the NIC • PCI bus is a 32-bit burst with a maximum rate of 132 MB/s • PCI-X is 64-bit wide and has a BW of 500 MB/s • AGP • High-speed graphic adaptor • Connected to the main memory • It is not a bus it can be connected to one device only • Has a BW of about 1 GB/s to the memory • AGP 2.0 can go up to 3.0 GB/s in BW • Legacy • ISA bus; low speed • For more information check my web: http://www.ccsu.edu/technology/farahmand/bhcosc/teaching.htm(3523)

14. Evaluating Server Components-Selecting a NIC

15. 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

16. 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

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. Recovery Plans • HD Failure • SW Failure • Electrical Problems • System Redundancy • Availability (clusters)

19. 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

20. Disk Redundancy through RAID • RAID 1 • Data is duplicated across two drives • Also called mirroring • If there are two adapters, it is called disk 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

21. 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

22. 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

23. 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

24. 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

25. Setting Up IP Addressing • IP addresses are divided into the network portion and the host portion • The subnet mask distinguishes the two portions

26. Common IP Classes

27. 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

28. 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