RAID is a storage architecture, not a backup. The RAID level determines how data and redundancy are distributed across the drives.
Practical example: choosing RAID for a file server
RAID availability and backup recovery solve different problems.
Scenario: A business file server needs usable capacity, reasonable write performance and tolerance for a drive failure.
RAID 0 would provide no redundancy, so it is unsuitable for this requirement. RAID 1 is simple but uses half of the raw capacity for mirroring. RAID 5 and RAID 6 introduce parity and different failure-tolerance and write-performance trade-offs. RAID 10 combines mirroring and striping but also has a significant capacity overhead.
Decision: Choose the RAID level from the workload, number of drives, rebuild risk, usable-capacity requirement and controller support. Then create a separate backup because RAID does not protect against deletion, corruption, malware or loss of the entire server.
Common mistakes and selection checklist
Common mistakes
- Selecting RAID only from the amount of usable capacity it provides.
- Ignoring rebuild time, drive count, write workload and the consequences of another drive problem during recovery.
- Treating RAID as a backup.
What happens if you get it wrong?
The array may have the wrong performance or resilience characteristics for the workload. A controller, corruption, deletion, malware event or complete system loss can still make the data unavailable even when the RAID level itself is working as designed.
Selection checklist
- Define the usable-capacity target and workload before selecting a RAID level.
- Check the minimum and practical drive count for the chosen layout.
- Consider write behaviour, rebuild exposure and failure tolerance.
- Verify controller, drive and server-platform support.
- Maintain a separate tested backup and recovery process.
A resilient array keeps services available during some drive failures. Separate backups provide recovery from deletion, corruption, malware and site loss.
RAID 0
RAID 0 stripes data across multiple drives. It can improve throughput and uses the combined capacity, but it provides no drive-failure redundancy.
RAID 1
RAID 1 mirrors data between drives. It provides redundancy at the cost of usable capacity.
RAID 5
RAID 5 uses striping with distributed parity and can tolerate a single drive failure in the array. Usable capacity is reduced by parity.
RAID 6
RAID 6 uses dual parity and can tolerate two drive failures in the array, with additional capacity used for parity.
RAID 10
RAID 10 combines mirroring and striping. It can provide strong performance and redundancy, but requires more drives and sacrifices capacity to mirroring.
| RAID | Primary characteristic | Failure protection |
|---|---|---|
| 0 | Striping | None |
| 1 | Mirroring | One drive in each mirror pair |
| 5 | Striping with parity | One drive |
| 6 | Striping with dual parity | Two drives |
| 10 | Mirroring plus striping | Depends on which drives fail |
A separate backup strategy is still required to protect against deletion, corruption, malware and other data-loss scenarios.
Confirm the exact product specification, supported configuration and compatibility before ordering. Platform generation, firmware, licences and optional components can change what a product supports.