Backup & Disk Mirroring
Protecting data is not just about stopping hackers; it is equally about ensuring data is not lost due to hardware failure, natural disasters, or human error. Organizations implement strict data retention strategies, including backups, archiving, and hardware-level redundancy like disk mirroring, to ensure high availability and security.
Learning Objectives
- 12.5.2.9 Describe data protection measures (data backup and disk mirroring)
Conceptual Anchor
The Spare Tire vs. The Photo Album
Disk Mirroring is like having four wheels on the back of a truck — if one tire blows out, the truck keeps driving without stopping (uninterrupted service). Data Backup is like keeping a spare tire in the trunk — if a tire blows, you have to stop and manually replace it to recover. Data Archiving is like taking old childhood photo albums and moving them to the attic — you don't need them every day, but you keep them safe to free up space in your living room.
Rules & Theory
1. Data Backup vs Data Archiving
A common misconception is that backups and archives are the same. They serve entirely different purposes in data management.
| Feature | Data Backup | Data Archiving |
|---|---|---|
| Purpose | Used as a data recovery tool to restore active data in case of accidental deletion, corruption, or hardware failure. | Intended to protect older information that is not needed for everyday operations but may have to be accessed occasionally. |
| Data State | A copy of active, currently used data. | Data that is not active but is too important to delete. |
| Primary Benefit | Ensures business continuity and disaster recovery. | A way of reducing primary storage and the related costs, rather than acting as a data recovery tool. |
A Best Practice: The 3-2-1 Backup Rule
- Keep 3 copies of your data (1 original + 2 backups).
- Store them on 2 different types of media (e.g., local hard drive and cloud storage).
- Keep 1 copy stored securely off-site (in case of fire or physical disaster).
2. Disk Mirroring & Fault Tolerance
Disk mirroring (also known as RAID-1 - Random Array of Independent Disks) is the practice of duplicating data in separate volumes on two hard disks simultaneously to make storage more fault-tolerant.
- How it works: Data is written simultaneously to two or more hard disks. Mirroring provides continuous data protection because data is constantly updated to both disks.
- Fault Tolerance: In the event of a disk failure, the computer automatically switches access to the next disk, without loss of data or interrupting data processing. Fault-tolerant technology is the capability of a computer system to deliver uninterrupted service, despite one or more of its components failing.
- Remote Sites: In some high-security configurations, backup disks are maintained at a remote site (mirror site) for additional safety against physical disasters.
Common Pitfalls
Mirroring is NOT a replacement for Backups
If you accidentally delete a file, or if a virus corrupts your data, Disk Mirroring will instantly copy that deletion or corruption to the second drive! Mirroring protects against hardware failure (fault tolerance). You still need Backups to protect against human error and malware.
Confusing Backup and Archiving
Backups are for your active files (acting as a data recovery tool). Archives are for your inactive files to free up primary storage space.
Exam Style Tasks
Define the term "Fault Tolerance" in the context of computer systems.
Describe how Disk Mirroring (RAID-1) operates during a hardware failure to prevent the interruption of data processing.
A school wants to free up space on its main server by moving students' graduated files from 5 years ago, but they cannot delete them. Would you recommend a Data Backup or Data Archiving solution? Justify your answer based on their distinct purposes.
Self-Check Quiz
Q1: What does RAID-1 stand for?
Q2: What is the main purpose of Data Archiving?
Q3: Why might an organization keep mirror disks at a remote site?