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Hardware and Software Basics

Christine S. Wolfe

Ohio University Lancaster

2008
-
Aug
-
01

Vocabulary:

This slide show introduces
hardware and software considerations for a web server.

Apache server

arithmetic logic unit

cache

client

client/server paradigm

CPU

end
-
to
-
End response

GET

hard drive

HTTP requests per second

Microsoft IIS (Internet Information Services)

NIC

payload

RAM

response time

server

Time to First Byte

web server

What are some of the things you need to take into consideration when buying a computer
or set of computers to use as a web server?

If you are hosting your website in
-
house (
ie
: on your premises) or if you have entered into a
co
-
location hosting agreement with a third party provider, you will have to obtain a computer
or set of computers on which to run your server.

Before you buy, you must determine how your server will function.

Purchase a system that has the features that best support the functions you will
implement.

Images and video require more storage space than do simple html text pages.

Dynamic pages require more processor power than do static pages.

High traffic sites require more bandwidth than do low traffic sites.

Unless you have unlimited funds, you will likely have to choose which options best suit your needs.

Computer hardware are the tangible parts of a computer system.

Hardware can be broken down into the following categories

Hardware

Input

Devices

Output

Devices

Volatile
Memory

Secondary
Storage

Processor


Structural

Components

keyboard

mouse

NIC

monitor

speakers

NIC

RAM

cache

hard drive

jump drive

ALU

case

power supply

fan

system board

The components that are most critical for server performance are:



Processor



Hard drives & other secondary storage capacity



RAM
and
Cache



Network Adapter(s)

We will discuss how these components influence server performance but we
won't worry about current specs. Any specs I would give you would be out of
date by the time you read it. If you understand what the component does then
you will know which are most important for your system and know where to
spend your money for the best benefit.

All that a computer really does is add.

Almost nothing happens in a computer without being processed as
a set of instructions + data sent through a processor. A processor
includes a) the arithmetic logic unit (ALU) where the instructions
are processed, b) registers to hold the instructions and data so the
ALU can grab them, and c) usually some cache.

Processor

Secondary storage is sometimes called permanent storage because data stored on a
secondary storage device doesn't disappear when the power is turned off. When you
"save" your work, you are writing a copy of it to secondary storage.


As far as your computer is concerned, your hard drive, a memory card, and a jump drive
all serve the same purpose. They have data that must be retrieved before the CPU can
work with it.

When choosing a hard drive or other
secondary storage device, you want to
consider how much it can hold and how
quickly it can find, read, and write data.












RAM

RAM stands for Random Access Memory. It is often referred to as "main" memory.

It can also be considered temporary memory because it cannot hold information unless it
has power.

Any time that your computer wants to work with data that is stored on a secondary
storage device such as your hard drive, a copy of the data must be read from the
secondary storage into RAM. Reading from RAM is much
much

much

faster than
reading from a hard drive so you would like to be able to store a large amount of data in
RAM. Factors to consider with RAM is the amount of storage and how efficiently it can
find and move data.

CPU












RAM

Level 1

(primary)

cache

ALU

Level 2

(secondary)

cache

Memory cache is a small, fast, set of memory located physically close to the ALU.

Cache
is used to temporarily store data that is likely to be needed in the near future
.

When the CPU orders data from main memory (RAM), the system will save the retrieved
data and some of the nearby data in a small cache that is more readily accessed. This
may reduce the retrieval time for future requests.

I need
red!

I need
green!

A network adapter is a piece of hardware
that allows the server to move data to
and from the Internet. It is possible to
install more than one adapter in a server.

As all the data that is being uploaded
and downloaded must pass through an
adapter, a high bandwidth capacity
adapter has a huge influence on the
speed of transmission.

We looked at 4 hardware components that are important considerations for server performance.

Processor,

Hard drive

RAM and Cache

Network Adapter(s)

Which 2 would give the best benefit to a server that
must perform a lot of calculations when creating
dynamic pages?

Which 1 would give the best benefit to a server that must
store a lot of images or other large files?

Which 1 would give the best benefit to a server that
experiences extremely high volumes of traffic?

On the midterm and final you will be expected to know
which component you would optimize based on the
purpose of a website.

Click

Tip

Software are the electronic instructions that cause the computer to retrieve, process, and
store data. Software is broken down into 2 categories:

Software

Operating

Software

Application
Software

Windows

Mac OS

Apache server

Word

Excel

Photoshop

An operating system (sometimes abbreviated as "OS") is the program that, after
being initially loaded into the computer by a boot program, manages all the other
programs in a computer. The other programs are called applications or application
programs. The application programs make use of the operating system by making
requests for services through a defined application program interface (API). ...

www.webasyst.net/glossary.htm

A web server (like most computers) must have an operating system.

A set of programs that control how the system works. Controls the running of
programs and provides such services as resource allocation, scheduling, input
and output control, and data management.

www.ncsa.uiuc.edu/UserInfo/Resources/Hardware/IBMp690/IBM/usr/share/man/in
fo/en_US/a_doc_lib/aixuser/glossary/O.htm

Apache server and Microsoft Internet Information Services are the dominant
web server operating systems.

Apache is free open source
software


Steep learning curve for most
effective use.


Large installed base with readily
available support from user
community
.


index.html is the home page that
opens if the user does not
specify a file name.



Internet Information Services is
proprietary software by Microsoft


Easy to install and use



Microsoft is a frequent target of
hackers and virus writers. Frequent
patches must be installed
.


default.html is the home page that
opens if the user does not specify a
file name.


Market Share for Top Servers Across All Domains August 1995


June 2010

http://news.netcraft.com/archives/2011/01/

Click Tip

This is a chart of SERVER types. Don't confuse it with the
browser and OS charts from the Unit 02 Browser Trends exercise.

OK, now we have all the "stuff" to make our web server.

How can we tell how well it's working?

Let's start with a review of what the web server is supposed
to do.

Web server and browsers are engaged in what is called a "client/server" relationship.
You get one guess which one is the server and which one is the client.


Of course the web server is the server


and just what is it serving up? Web pages!

The server sits out there in the cloud with a belly full of web pages just waiting for
some browser to ask for one of them. The server is patient and will sit and wait forever
as long as it has power.

When a user requests a page via a browser, only then does the browser go out and
find the server and ask it for a page.

It is in response to this request that the server really goes into action. This is when
you as the web site owner want the server to perform its very best. You want it to
provide the page that was requested and to provide it as quickly as possible.

The Client/Server Paradigm

1.
The server starts and waits

2.
The client initiates contact via a request for a service

3.
The client and server exchange messages (data, files, etc)

4.
They both agree to end the exchange

SERVER

CLIENT

I want what you have

Come and
get it! Get
your web
pages here.

Here you go.

Thanks.

That's all I need.

OK. Bye

Have you ever tried to go to a web page


only to have the following message show up on your screen?

See the next
slide to learn
where this
comes from.

When the client browser contacts the server, it sends a GET message.

The server sends a response code that let's the client browser know if it is able to send the page.

The codes are categorized by their first digit.

Successful 2xx
: This class of status code indicates that the client's
request was successfully received, understood, and accepted
eg
: 200 OK

Informational 1xx
: This class of status code indicates a provisional
response, consisting only of the Status
-
Line and optional headers, and is
terminated by an empty line.
eg
. 100 Continue

A complete listing can be found at: http://www.w3.org/Protocols/rfc2616/rfc2616
-
sec10.html

Redirection 3xx:

This class of status code indicates that further action
needs to be taken by the user agent in order to fulfill the request.
eg
: 301
Moved Permanently

Client Error 4xx:

The 4xx class of status code is intended for cases in
which the client seems to have erred.
eg

404 Not Found

Server Error 5xx
": Response status codes beginning with the digit "5"
indicate cases in which the server is aware that it has erred or is
incapable of performing the request.
eg
: 505 HTTP Version Not
Supported








Assuming your web server has the page or knows how to make the page and wants to
send it to the client browser, how can you measure how well it is
performing?Measure

the responsiveness of a web site during peak periods.

HTTP requests per second

The following are 3 common metrics for evaluating server responsiveness.

the number of GET requests that the server
responds to in one second

Click

Tip

Always measure performance during peak usage.

Go!

Stop!








End
-
to
-
End response

how long it takes from the time a GET request
is received and the time the last byte of the
requested document is delivered..

Start
Timing

Stop

Timing








Time To First Byte

how long it takes from the time a GET request
is received and the time the first byte of the
requested document is delivered..

Start
Timing

Stop

Timing

Works Cited

1.

HTTP: The Definitive Guide
by
David Gourley
;
Brian Totty Publisher:
O'ReillyPub Date:
September 2002

ISBN:
1
-
56592
-
509
-
2
Pages:
656 Chapter
5. Web Servers

2.

http://www.dba
-
oracle.com/t_best_webserver_hardware_configuration.htm.


What is the best webserver hardware configuration?


Web Tips by Burleson Consulting

3.

http://www.seoconsultants.com/articles/1000/cache
-
control.asp


What Is Caching and How Does It Apply to the Web?

4. http://news.netcraft.com/archives/web_server_survey.html