3.2.2 - Utility software
A corrupted file, a failed drive and a slow magnetic hard disk do not need the same fix. This lesson makes the five utilities in 3.2.2 precise enough for you to choose one and explain how its action solves a stated problem.
Utility software and file repair
Utility software
A collection of software tools that helps to maintain the functionality of a computer system.
A utility performs a focused maintenance or protection task. The right choice depends on the problem: repairing damaged data, restoring a copy, reducing file size, reorganising HDD blocks or detecting malware.
Imagine that a computer loses power while a media-project file is being saved. The file now gives a corruption error and will not open. Corrupted data has been damaged or left in an inconsistent form, so software cannot interpret it correctly.
File repair software
A utility that attempts to repair damaged or corrupted files, or recover readable data from them.
The utility can inspect the file or the storage information that describes it, correct structures it recognises as invalid, and salvage data that is still readable. Recovery is not guaranteed: some damaged data may no longer be available.
Worked situation: There is no separate copy of the media project. File repair is the appropriate first choice because it acts on the damaged file and may make the file usable or recover part of its contents. Backup software cannot recreate an earlier copy that was never backed up.
Repair attempts to fix or recover damaged data. Restore retrieves a separate copy made earlier.
Full and incremental backups
Backup software
A utility that automates making separate copies of selected data so that the data can be restored if the original is lost, damaged or corrupted.
A useful backup keeps a recoverable version separate from the working data. Moving the only copy to another drive is not a backup. A live copy that immediately repeats every deletion or corruption may also fail to preserve the earlier version that is needed.
There are two required backup types:
| Backup type | What is copied | Consequence |
|---|---|---|
| Full | All selected files and data | Takes more time and storage to create, but provides a complete baseline and is simpler to restore. |
| Incremental | Only selected data that is new or has changed since the most recent backup | Usually quicker and smaller to create, but restoration needs the latest full backup and every later incremental backup in order. |
Worked backup sequence: A school stores three selected files: plan, poster and video.
| Day | Changes since the previous backup | Backup made | Data copied that day |
|---|---|---|---|
| Friday | Starting point | Full | plan, poster, video |
| Saturday | poster changed; audio created | Incremental | poster, audio |
| Sunday | plan and video changed | Incremental | plan, video |
To restore the Sunday state, the utility first restores Friday's full backup, then applies Saturday's incremental changes, then Sunday's incremental changes. Skipping Saturday would lose the new audio file and Saturday's version of poster.
Incremental backups reduce repeated copying, but the saving during backup creates a dependency chain during restore.
Data compression
Data compression software
A utility that encodes data using a smaller representation so that the resulting file uses less storage space.
A compression utility reads the original data, finds a more compact way to represent it and writes a compressed file. Most programs cannot use a compressed archive directly, so a decompression operation reconstructs its files before ordinary use. Merely renaming a file with a compressed-file extension does not compress its data.
Compression has two important purposes in this lesson:
- the compressed file occupies less storage space;
- less data needs to be transmitted, so transfer can take less time on the same connection.
Worked situation: A folder of project resources occupies 800 MB. A compression utility produces a 260 MB archive. Storing the archive uses 540 MB less space, and sending 260 MB requires less data to cross the network than sending 800 MB. The recipient decompresses the archive to use the project files.
Compression does not increase the physical capacity of the storage device and it is not the same as deleting unwanted files. It changes how the selected data is represented.
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