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 processor

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 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 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 64 66 MHz UltraSPARC IIi 2 MB 4 UltraSPARC IIe 256 KB

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

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

Evaluating Server Components- Selecting a NIC NIC Type Speed Media Use Standard Ethernet 10 Mbps Twisted pair (sometimes fiber) Workstations Fast 100 Mbps Workstations and small to medium servers Gigabit 1,000 Mbps Fiber (sometimes twisted pair) High-end servers 10-Gigabit 10,000 Mbps Fiber Backbone connections ATM 25 Mbps – 622+ Mbps servers (rare)

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 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 open

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 users on the internal network

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