1. Lesson Objectives Aims You should be able to:
Define and describe the following types of utility:
Encryption software
Defragmentation
Data compression
Describe the role and methods of backup:
Full Backups
Incremental Backups

2. Utility A Utility is… Such as: Software
Which performs one specific task
Usually to do with system maintenance or upkeep
Usually in the background or with little user intervention
Such as:
Defragmentation
Anti Virus
Compression or disk utilities

3. Encryption has been well covered in the Networking lessons
Key points to recap:
Encryption – Purpose? Meaning?
Asymmetric encryption
Encryption keys
What happens if data is stolen/copied/intercepted

4. An encryption utility will clearly:
Encrypt files or entire drives
Provide security in the event of theft or accidental loss
Do so without user intervention
Be based on a password or biometrics for the key
Think about where drive/file encryption would be necessary…

5. Defrag This is becoming old hat now
This only applies to magnetic hard drives and also certain file systems
Modern SSD drives do not suffer from fragmentation
Instead they need TRIMming now and again

6. Defrag Files get moved or deleted on disk This leaves gaps
A file system may try to fill these gaps causing…
Some files to not quite fit
Which leaves either small bits of unused storage or..
…the need to split a file physically across the disk
This leads to slower access times
Defrag tries to put all data logically in order on the disk with no gaps
And all files stored contiguously.

7. Data Compression Compression is: Needed to:
Reducing the size of a file (number of bytes, KB or MB it takes up) through the removal of unnecessary or redundant data
Needed to:
Reduce the amount of data to transfer (or store)
Speed up data transfer
Reduce bandwidth used

8. When compressing you have a choice:
Methods
When compressing you have a choice:
Make it so you can reproduce the original file EXACTLY (LOSSLESS compression) Or
Make it so you can reproduce a close approximation (good enough version) of the original file (LOSSY compression)

9. Lossless compression is the equivalent of folding up a piece of paper:
It’s smaller than it was
But nothing has been taken away
This is essential if:
You are compressing text!
You need to be able to reproduce the original file
You want to maintain the highest quality of image, sound, video.

10. Lossless Lossless advantages: Disadvantages: Examples:
You still reduce the file size (but often not as much as using lossy compression)
You can reproduce the original EXACTLY
No quality or information is lost
Disadvantages:
It takes up more space (usually)
Examples:
PNG, FLAC, DOCX

11. Lossy compression throws away unnecessary data to save space:
Sounds/frequencies you can’t hear
Colour data that can be interpolated
But this does mean you can only create an approximation of the original
You can NEVER get the original data back once it’s been compressed

12. Lossy Lossy advantages: Disadvantages: Examples:
You get a much smaller file size, ideal for transmission
You can still understand what the original looked/sounded like
Disadvantages:
You can never get the original data back
It cannot be used for text or where you need the highest quality
Too much lossy compression results in very poor quality – think about streaming videos on a poor connection.
Examples:
JPG, MP3, GIF

13. Lossless V Lossy – spot the difference

14. Backup A backup is: For the purpose of: An exact copy of data
Stored externally from the original
On removable media
For the purpose of:
Disaster recovery
Recovery from user error/mistakes
Ability to restore to an exact point in time

15. Backups come in two flavours:
Full
Incremental
I bet you can’t guess the difference…
This is Mr Flavour. No really. Apparently he’s worth millions.

16. Full backups
A full back up takes a copy of the ENTIRE disk/file structure to be backed up
This is good because:
Nothing is missed out
You can restore an entire machine back to a certain point in time
But not efficient because:
It takes up a shed load of storage space…
…which is expensive
And takes a LONG time (overnight)

17. Incremental backups This is the sensible version of backup:
Take a FULL backup first
Then, every day or whenever you do a new backup…
…Simply back up only the files which have changed or are new
This is clearly a good idea because:
Each daily backup will be much smaller than a full backup
It will be much cheaper in terms of storage
The data will be backed up quicker
It should be quicker to access files that have been backed up

18. Media Backups are large and have to go somewhere:
Tape (still the most common form)
Hard Drives or similar mass external storage (reliability?)
More commonly – the cloud.
Each has its obvious advantages and disadvantages – what can you come up with now?
Think cost, physical space, security