Transcript Powerpoint - Chapter 14

Chapter Overview



Determining Network Needs
Providing Fault Tolerance
Collecting Essential Information
1
Why Does the Organization Want a
New Network Installed?



You might be providing a network for a new
installation that has no existing equipment.
You might be asked to network a group of
existing stand-alone computers.
The organization might have an existing
network that it wants to upgrade to a new or
different technology.
2
What Services Does the Organization
Want the Network to Provide?



At the most basic level, organizations usually
want their users to be able to access shared
drives and printers and connect to the
Internet.
Heads of organizations and users often know
what they want in a network but do not
understand the technical requirements and
implementation issues.
In addition to talking to the heads of
organizations, it is a good idea to talk with
the people who will use the network.
3
Evaluating the Installation Site

A proper site evaluation helps you to choose



What type of network to install
What network medium to use
How to install the network
4
Evaluating Distances Between
Components




Know the maximum distances supported by
the protocols you will use.
Consider the actual route that your cables will
take, not just the distance between the
components.
Consider the obstacles between the
computers that will be connected to the
network.
Determine where to put the back-end
components, such as hubs, servers, and
routers.
5
Ergonomics

Planning a network includes


Selecting equipment designs that are suitable for
the working environment
Placing equipment where it will be most useful
and cause the least distraction
6
Environmental Conditions





Be conscious of the climate conditions at all equipment
locations and at all times of day.
A data center containing a large number of computers,
routers, and other heat-producing devices will probably
need an independent climate control system to keep the
room cool enough.
Make sure a source of clean, consistent electrical power is
available.
Some networks are exposed to extreme environments,
such as outdoors or industrial areas that expose the
equipment to abnormal amounts of heat or cold, humidity,
dust, electromagnetic interference, or chemical vapors.
Some products enable computers to operate in extreme
conditions.
7
Sources of Interference



For internal cable installations, examine the
anticipated cable locations and routes for possible
obstructions and sources of interference.
Keep in mind that copper-based cables are highly
susceptible to electromagnetic fields caused by
fluorescent light fixtures, electric motors, and other
types of electrical equipment.
Use cable routes that avoid sources of interference.


If proper routes are not available, you might have to use
cable with additional shielding, or even fiber optic cable,
which is not affected by electromagnetic interference.
Be aware of local fire and building codes for cabling.
8
Selecting Hardware




For a new network installation, you should select
computers that can fully support the networking
tasks expected of them.
If networking existing computers, you should
consider their age and whether you need to
upgrade them by adding memory or disk space.
Compatibility is crucial when working with
existing equipment—either an existing network
or a group of stand-alone computers.
Many hardware purchasing decisions you make
are based on the protocols you choose to run,
especially at the data-link layer.
9
What Is Fault Tolerance?




Depending on the organization, an equipment
failure or other service interruption can mean lost
productivity, lost revenue, and sometimes lost
lives.
Fault-tolerance mechanisms enable a computer
or a network to continue operating despite the
failure of a major component.
When network functions are absolutely critical,
the fault-tolerance mechanisms can be elaborate.
In most cases, however, fault-tolerance
mechanisms protect only a few key components
from outages due to hardware or software faults.
10
Mirroring

Mirroring is an arrangement in which two identical hard
drives connected to a single host adapter always contain
identical data.





The two drives appear to users as one logical drive.
Whenever users save data to the mirror set, the computer writes it
to both drives simultaneously.
If one hard drive unit fails, the other takes over immediately until
the malfunctioning drive is replaced.
Many operating systems, including Microsoft Windows
2000, Microsoft Windows NT, and Novell NetWare, support
disk mirroring.
Disk mirroring has two main drawbacks:


The server provides only half of its available disk space to users.
Although mirroring protects against a drive failure, a failure of the
host adapter or the computer can still render the data unavailable.
11
Duplexing



Disk duplexing provides a higher degree of
data availability than mirroring because it
uses duplicate host adapters as well as disk
drives.
Identical disk drives on separate host
adapters maintain exact copies of the same
data, creating a single logical drive.
Duplexing allows the server to survive either
a disk failure or a host adapter failure and still
make its data available to users.
12
Volumes


A volume is a fixed amount of data storage space
on a hard drive or other storage device.
On a network server, you can create




Multiple volumes on a single drive
A single volume from multiple drives (a technique
called drive spanning)
You can use drive spanning to make all storage
space on multiple drives in a server appear as a
single entity.
The drawback of drive spanning is that if one of
the hard drives containing part of the volume
fails, the whole volume is lost.
13
Disk Striping




Disk striping is a method in which you create a
single volume by combining the storage on two
or more drives and writing data alternately to
each one.
The computer splits each file into multiple
segments and writes alternate segments to each
disk.
Striping speeds up data access by enabling one
drive to read a segment while the other drive’s
heads are moving to the next segment.
If one drive in the stripe set fails, the entire
volume is lost.
14
RAID




Redundant array of independent disks (RAID) is a comprehensive data
availability technology with various levels that provide all of the
functions of mirroring, duplexing, volumes, and disk striping.
Higher RAID levels store error correction information along with the
data, so that even if a drive in a RAID array fails, its data still remains
available from the other drives.
Although RAID is available as a software product that works with
standard disk drives, many high-end servers use dedicated RAID drive
arrays, which

Consist of multiple hard drive units in a single housing

Often have hot swap capability
Hot swapping is the ability to remove and replace a malfunctioning
drive without shutting off the other drives in the array, so the data is
continuously available to network users during the drive repair.
15
RAID Levels
Level Technology
Function
0
Disk striping
Enhances performance by writing data to multiple disk drives,
one block at a time; provides no fault tolerance.
1
Disk mirroring and
duplexing
Provides fault tolerance by maintaining duplicate copies of all
data on two drives. Disk mirroring uses two drives connected
to the same host adapter, and disk duplexing uses two drives
connected to different host adapters.
2
Hamming errorcorrecting code
(ECC)
Ensures data integrity by writing error-correcting code to a
separate disk drive; rarely implemented.
3
Parallel transfer
with shared parity
Provides fault tolerance by striping data at the byte level
across a minimum of two drives and storing parity information
on a third drive. If one of the data drives fails, its data can be
restored by using the parity information.
16
RAID Levels (Cont.)
Level Technology
Function
4
Independent data
disks with shared
parity
Identical to RAID 3, except that the data is striped across the
drives at the block level.
5
Independent data
disks with
distributed parity
Provides fault tolerance by striping both data and parity
across three or more drives instead of using a dedicated
parity drive, as in RAID 3 and RAID 4.
6
Independent disks
with twodimensional parity
Provides additional fault tolerance by striping data and two
complete copies of the parity information across three or
more drives.
7
Asynchronous
RAID
Proprietary hardware solution that consists of a striped data
array and a separate parity drive, plus a dedicated operating
system that coordinates the disk storage activities.
17
RAID Levels (Cont.)
Level Technology
Function
10
Striping of
mirrored disks
Combines RAID 0 and RAID 1 by striping data across mirrored
pairs of disks, thus providing both fault tolerance and
enhanced performance.
53
Striped array of
arrays
Stripes data across multiple RAID 5 arrays, providing the
same fault tolerance as RAID 5 with additional performance
enhancement.
0+1
Mirroring of striped Combines RAID 0 and RAID 1 in a different manner by
disks
mirroring the data stored on identical striped disk arrays.
18
NAS



Network attached storage (NAS) uses a
dedicated storage appliance that connects
directly to the network and contains its own
embedded operating system.
NAS is essentially a multiplatform file server.
Computers on the network can access the
NAS appliance in a variety of ways.
19
SANs



A Storage Area Network (SAN) is a separate
network installed at a local area network
(LAN) site that connects servers to disk arrays
and other network storage devices.
SANs make it possible to use dedicated
storage hardware arrays without overloading
the client network with storage-related traffic.
SANs typically use the Fibre Channel protocol
to communicate, but they can theoretically
use any network medium and protocol.
20
Novell NetWare SFT III


NetWare SFT III was one of the first
commercially successful server duplication
technologies.
NetWare SFT III is a version of NetWare that
consists of two copies of the network operating
system, plus a proprietary hardware connection
that links the two separate server computers.



The servers run an application that synchronizes their
activities.
For example, when a user saves data to one server
volume, the data is written to both servers at the same
time.
If one of the servers should malfunction for any
reason, the other server instantly takes its place. 21
Novell NetWare SFT III Connects Two
Servers
22
Clustering


Clustering is a technique for interconnecting multiple
computers to form a unified computing resource and
provide fault tolerance.
A cluster can also




Distribute the processing load for specific tasks among the various
computers
Balance the processing load by allocating client requests to
different computers in turn
To increase the cluster’s speed and efficiency, you can
connect another computer to the group to add its
capabilities to those of the others.
Both Microsoft and Novell support clustering.


Microsoft Windows 2000 Advanced Server and Microsoft Windows
NT 4.0 Enterprise Edition
Novell NetWare Cluster Services for NetWare 5.1
23
Servers Connected in a Cluster
24
Network Redundancy
25
Standardizing Workstation
Configurations


Creating a standard workstation configuration simplifies the
troubleshooting process, because all of the computers are
functionally the same.
A workstation configuration can include any or all of the
following elements:








Which applications are installed
Where the applications are installed
Where the users will store data files
Drive letter mappings for shared network drives
Local drive sharing parameters
Printer connections
The ideal situation is to make new workstations completely
identical, except for parameters that must be unique.
If several users have different requirements, you might need to
create several different workstation configurations.
26
Factors in Selecting IP Addresses





How many computers are there?
How many network segments are there?
Will you connect the network to the Internet?
If you will connect the network to the
Internet, how will you do it?
Will your new computers interact with
existing computers?
27
Additional TCP/IP Configuration
Issues



What routers should your workstations use as
their default gateways?
Which Domain Name System (DNS) servers
should the workstations use?
Should you run Windows Internet Name
Service (WINS)?
28
Creating Accounts

To assign computer names and account names, develop a
formula and stick to it.





You can create computer names that use codes to represent the
subnet the computer is on or the physical location of the computer
in the building.
Do not assign computer names based on the names of their users
because you do not want to change the name whenever someone
new uses the computer.
To assign user account names, you can combine the user’s
initials and several letters of the first and last name.
Set a policy for the administrative accounts for your
network.
Decide which groups or organizational units you want to
create to administer the accounts most efficiently.
29
Chapter Summary

Determining network needs




Consult with both management and staff to
determine what network services are required.
Evaluate the site where the network will be to
determine what type of hardware to install, what
network medium to use, and how to install the
network.
Check distances between network components,
environmental conditions, local building codes,
and possible sources of structural and
electromagnetic interference.
Select network hardware carefully to ensure that
all products are compatible.
30
Chapter Summary (Cont.)

Providing fault tolerance



Networks use a variety of data storage techniques to
increase the efficiency and fault tolerance of the network
storage subsystem.
Creating redundant paths through the network enables
communications to continue, even if a cable breaks or a
router fails.
Collecting essential information



Creating standard workstation configurations simplifies the
process of supporting the computers later.
Before installing the network, you must decide what Internet
Protocol (IP) addresses you will use and how you will assign
them.
The best way to assign computer names and user account
names is to develop a formula and use it consistently. 31