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

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

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

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…

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

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.

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

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)

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.

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

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

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

Lossless V Lossy – spot the difference

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

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.

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)

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

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