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1.     Introduction and Feasibility

2.     Network Needs and Analysis

3.     Global Media & Communications (1stGMC)

4.     Network services : local area networks

5.     Network services : wide area networks

6.     DHCP

7.     WinRoute

8.     Default Gateway

9. DNS

10. Building Cabling

10.1.                    Introduction

10.2.                    Standards

11. Topology

12. Telecommunications Closet

13. Dell Blade Server

14. Cisco Router

15. Catalyst 2950 Series Switch

16. Catalyst 3550 Series Switch

17. Cisco Micro Hub 1538 Hub – 8 Port

18. APC Smart-UPS 500VA USB & Serial 100V Black

19. Firewall

20. Network services : voice over ip

21. Network services : replication

22. ModernGraphics.Com

23. Cost-Benefit Analysis


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data storage : raid

RAID stands for Redundant Array of Inexpensive (or sometimes "Independent") Disks. RAID is a method of combining multiple hard disks in a single logical unit to offer high availability, performance or a combination of both. This provides better resilience and performance than a single disk drive.

benefits of RAID

software RAID

Many operating systems provide functionality for implementing software based RAID systems . The software RAID systems generate the RAID algorithms using the server CPU, this can severely limit the RAID performance. Should a server fail the whole RAID system is lost. Cheap to implement and only need a single SCSI controller.

hardware RAID

All RAID algorithms are generated on the RAID controller board, thus freeing the server CPU. Allows full benefits and data protection of RAID. More robust and fault tolerant than software RAID. Requires dedicated RAID controller to work.

RAID Levels

Various RAID levels exist these are:


The levels of RAID protection varies with the RAID level selected RAID levels 0 is not technically RAID as they have no redundancy in the event of drive failure.

JBOD Subsystems

These JBOD subsystems are high-density storage enclosures that can be cond to specific applications including changes to disk drive form factor and number of drives per enclosure.

This includes configurations of 8, 12, 14, 16 disk drives per enclosure.

RAID Features:

Write Through Cache

With Write Through Cache the data is written to both the cache and drive once the data is retrieved.

As the data is written to both places, should the information be required it can be retrieved from the cache for faster access.

The downside of this method is that the time to carry out a Write operation is greater the time to do a Write to a non cache device. The total Write time is the time to write to the cache plus the time to Write the disk.

Write Back Cache

With Write Back Cache the write operation does not suffer from the Write time delay.

The block of data is initially written to the cache, only when the cache is full or required is the data written to the disk.

The limitation of this method is that the storage device for a period of time does not contain the new or updated block of data.

If the data in the cache is lost due to power failure the data cannot be recovered.

When using Write Back Cache a battery backup module would prevent data loss in a RAID power failure.

Battery Backup

Provides data recovery in the event of power failure. Should the RAID controller fail the battery backup module can be transported to the replacement RAID controller and everything will continue.

A downside of battery backup modules is they loose their capacitance over time, need replacing every 12-24 months, add to the RAID cost and only hold the information for up to 72 hours.

Hot Swap

Whenever a RAID system mentions hot swap, the components can replaced while the RAID continues to operate.

Online Hot Spare

Should a drive fail within the RAID it will automatically utilise the hot spare and carry out a RAID re-build.

These can be of two types a). Local hot spare is available only to a specified RAID set.

b). Global hot spare can be available to multiple RAID sets.

Read Ahead Caching

A buffering technique used by hard disk drives and other disk access devices, in which extra data beyond that requested by the system is read and stored in cache memory.

There is a strong chance, especially when dealing with sequential data, that this subsequent information will also be requested by the computer.

Reading from cache memory is much faster than reading from the disk or media, so read-ahead caching speeds increase overall system performance to a degree. Also called look-ahead caching.

Online Capacity Expansion

The primary reason for Online Capacity Expansion is that it allows disk drives to be added to RAID systems whilst operating.

These disk drives can then be used to grow the overall RAID capacity, without taking anything offline.

The traditional method would be to backup the information and then destroy the RAID set and build a new RAID from scratch.


This specification defines a set of SCSI commands for setting drive status information, including status for RAID arrays, into a disk drive array enclosure.

The drive array enclosure may be a separate enclosure, or the same enclosure.

The specification also defines commands for managing hot-swap drive slots and returning environmental health information for a drive enclosure.

The status commands are typically used by the enclosure manufacturer to assert lights or other indicators that provide information to the user about the state of the drives in the array.

This can include status such as 'rebuilding', 'fault', and 'hot spare'. The SAF-TE status setting commands are typically issued either by an intelligent disk controller, or by software, e.g. RAID software , running under the operating system.

Other parties on the SCSI bus may elect to access the status information as a means of determining the state of the physical drives in the array.

In addition, SAF-TE commands can be used to report certain environmental information about the enclosure, such as temperature, voltage, power supply, and fan health.


SMART - Self-Monitoring Analysis and Reporting Technology

The fundamental principle behind SMART is that many problems with hard disks don't occur suddenly.

They result from a slow degradation of various mechanical or electronic components.

SMART evolved from a technology developed by IBM called Predictive Failure Analysis or PFA. PFA divides failures into two categories: those that can be predicted and those that cannot. Predictable failures occur slowly over time, and often provide clues to their gradual failing that can be detected.

An example of such a predictable failure is spindle motor bearing burnout: this will often occur over a long time, and can be detected by paying attention to how long the drive takes to spin up or down, by monitoring the temperature of the bearings, or by keeping track of how much current the spindle motor uses.

An example of an unpredictable failure would be the burnout of a chip on the hard disk's logic board: often, this will "just happen" one day.

Clearly, these sorts of unpredictable failures cannot be planned for.

RAID Stripe

As a rule a Stripe size can be anything from 2k to 512k or greater (depends on controller support).

There is no rule to the recommended Stripe size, it depends entirely on the application and performance needs.

For example large numbers of small reads and writes are probably better off with small stripe sizes, applications where smaller numbers of larger files need to be read quickly will likely prefer large stripes.

At the end of the day it is trial and error.

RAID Rebuild

This is when a RAID system suffers a drive. During a RAID re-build performance is degraded, in order for it to work out where the Data and Parity bit should be written.


RAID Level 0 requires a minimum of 2 drives to implement

Characteristics & Advantages

RAID 0 implements a striped disk array, the data is broken down into blocks and each block is written to a separate disk drive I/O performance is greatly improved by spreading the I/O load across many channels and drives

Best performance is achieved when data is striped across multiple controllers with only one drive per controller

No parity calculation overhead is involved

Very simple design

Easy to implement


Not a "True" RAID because it is NOT

The failure of just one drive will result in all data in an array being lost

Should never be used in mission critical environments

Recommended Applications

  • Video Production and Editing

  • Image Editing

  • Pre-Press Applications

  • Any application requiring high bandwidth

For Highest performance, the controller must be able to perform two concurrent separate Reads per mirrored pair or two duplicate Writes per mirrored pair. RAID Level 1 requires a minimum of 2 drives to implement

Characteristics & Advantages

One Write or two Reads possible per mirrored pair

Twice the Read transaction rate of single disks, same Write transaction rate as single disks

100% redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk

Transfer rate per block is equal to that of a single disk

Under certain circumstances, RAID 1 can sustain multiple simultaneous drive failures

Simplest RAID storage subsystem design


Highest disk overhead of all RAID types(100%) - inefficient

Typically the RAID function is done by system software, loading the CPU/Server and possibly degrading throughput at high activity levels. Hardware implementation is strongly recommended

May not support hot swap of failed disk when implemented in "software"

Recommended Applications

  • Accounting

  • Payroll

  • Financial

  • Any application requiring very high availability


Each bit of data word is written to a data disk drive (4 in this example: 0 to 3). Each data word has its Hamming Code ECC word recorded on the ECC disks. On Read, the ECC code verifies correct data or corrects single disk errors.

Characteristics & Advantages

"On the fly" data error correction

Extremely high data transfer rates possible

The higher the data transfer rate required, the better the ratio of data disks to ECC disks

Relatively simple controller design compared to RAID levels 3,4 & 5


Very high ratio of ECC disks to data disks with smaller word sizes - inefficient

Entry level cost very high - requires very high transfer rate requirement to justify

Transaction rate is equal to that of a single disk at best (with spindle synchronization)

No commercial implementations exist / not commercially viable


The data block is subdivided ("striped") and written on the data disks. Stripe parity is generated on Writes, recorded on the parity disk and checked on Reads. RAID Level 3 requires a minimum of 3 drives to implement

Characteristics & Advantages

Very high Read data transfer rate

Very high Write data transfer rate

Disk failure has an insignificant impact on throughput

Low ratio of ECC (Parity) disks to data disks means high efficiency


Transaction rate equal to that of a single disk drive at best (if spindles are synchronized)

Controller design is fairly complex

Very difficult and resource intensive to do as a "software" RAID

Recommended Applications

  • Video Production and live streaming

  • Image Editing

  • Video Editing

  • Prepress Applications

  • Any application requiring high throughput


Each entire block is written onto a data disk. Parity for same rank blocks is generated on Writes, recorded on the parity disk and checked on Reads. RAID Level 4 requires a minimum of 3 drives to implement.

Characteristics & Advantages

Very high Read data transaction rate

Low ratio of ECC (Parity) disks to data disks means high efficiency

High aggregate Read transfer rate


Quite complex controller design

Worst Write transaction rate and Write aggregate transfer rate

Difficult and inefficient data rebuild in the event of disk failure

Block Read transfer rate equal to that of a single disk


Each entire data block is written on a data disk; parity for blocks in the same rank is generated on Writes, recorded in a distributed location and checked on Reads.

RAID Level 5 requires a minimum of 3 drives to implement.

Characteristics & Advantages

Highest Read data transaction rate

Medium Write data transaction rate

Low ratio of ECC (Parity) disks to data disks means high efficiency

Good aggregate transfer rate

Recommended Applications


Disk failure has a medium impact on throughput

Most complex controller design

Difficult to rebuild in the event of a disk failure (as compared to RAID level 1)

Individual block data transfer rate same as single disk.


Two independent parity computations must be used in order to provide protection against double disk failure. Two different algorithms are employed to achieve this purpose.

RAID Level 6 requires a minimum of 4 drives to implement.

Characteristics & Advantages

RAID 6 is essentially an extension of RAID level 5 which allows for additional fault tolerance by using a second independent distributed parity scheme (dual parity)

Data is striped on a block level across a set of drives, just like in RAID 5, and a second set of parity is calculated and written across all the drives; RAID 6 provides for an extremely high data fault tolerance and can sustain multiple simultaneous drive failures

Perfect solution for mission critical applications

Recommended Applications


More complex controller design

Controller overhead to compute parity addresses is extremely high

Write performance can be brought on par with RAID Level 5 by using a custom ASIC for computing Reed-Solomon parity

Requires N+2 drives to implement because of dual parity scheme


RAID Level 10 requires a minimum of 4 drives to implement

Characteristics & Advantages

RAID 10 is implemented as a striped array whose segments are RAID 1 arrays

RAID 10 has the same fault tolerance as RAID level 1

RAID 10 has the same overhead for fault-tolerance as mirroring alone

High I/O rates are achieved by striping RAID 1 segments

Under certain circumstances, RAID 10 array can sustain multiple simultaneous drive failures

Excellent solution for sites that would have otherwise gone with RAID 1 but need some additional performance boost


Very expensive / High overhead

All drives must move in parallel to proper track lowering sustained performance

Very limited scalability at a very high inherent cost

Recommended Applications


RAID Level 50 requires a minimum of 6 drives to implement

Characteristics & Advantages

RAID 50 should have been called "RAID03" because it was implemented as a striped (RAID level 0) array whose segments were RAID 3 arrays(during mid-90s)

Most current RAID 50 implementation is illustrated above

RAID 50 is more fault tolerant than RAID 5 but has twice the parity overhead

High data transfer rates are achieved thanks to its RAID 5 array segments

High I/O rates for small requests are achieved thanks to its RAID 0 striping

Maybe a good solution for sites who would have otherwise gone with RAID 5 but need some additional performance boost


Very expensive to implement

All disk spindles must be synchronized, which limits the choice of drives

Failure of two drives in one of the RAID 5 segments renders the whole array unusable

RAID 0 + 1

RAID Level 0+1 requires a minimum of 4 drives to implement

Characteristics & Advantages

RAID 0+1 is implemented as a mirrored array whose segments are RAID 0 arrays

RAID 0+1 has the same fault tolerance as RAID level 5

RAID 0+1 has the same overhead for fault-tolerance as mirroring alone

High I/O rates are achieved thanks to multiple stripe segments

Excellent solution for sites that need high performance but are not concerned with achieving maximum reliability


RAID 0+1 is NOT to be confused with RAID 10. A single drive failure will cause the whole array to become, in essence, a RAID Level 0 array

Very expensive / High overhead

All drives must move in parallel to proper track lowering sustained performance

Very limited scalability at a very high inherent cost

Recommended Applications

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