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RAID (Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical hard drives or SSDs into a single logical unit. RAID improves performance, fault tolerance, or both, depending on the RAID level used.
Types of RAID and Their Descriptions
1. RAID 0 (Striping)
- Description: Data is split across multiple disks for increased speed.
- Advantages: High read/write performance, full disk space utilization.
- Disadvantages: No redundancy; failure of a single disk results in total data loss.
2. RAID 1 (Mirroring)
- Description: Data is duplicated across two disks for redundancy.
- Advantages: High reliability; if one disk fails, data remains intact on the other.
- Disadvantages: Only 50% storage efficiency since one disk is a complete copy.
3. RAID 5 (Striping with Parity)
- Description: Data is striped across multiple disks with parity information distributed among them.
- Advantages: Fault tolerance (can withstand one disk failure), good read speed.
- Disadvantages: Write performance is slower due to parity calculations.
4. RAID 6 (Striping with Double Parity)
- Description: Similar to RAID 5 but with two parity blocks for extra redundancy.
- Advantages: Can tolerate up to two disk failures, making it more reliable.
- Disadvantages: Slower writes due to double parity calculation, more storage overhead.
5. RAID 10 (1+0) (Mirrored Striping)
- Description: Combination of RAID 1 and RAID 0; data is mirrored and then striped.
- Advantages: High performance and redundancy; can survive multiple disk failures.
- Disadvantages: Requires at least four disks, expensive due to mirroring.
6. RAID 50 (5+0)
- Description: Combination of RAID 5 and RAID 0; RAID 5 arrays are striped.
- Advantages: Better redundancy and performance than RAID 5 alone.
- Disadvantages: Requires a minimum of six disks, complex setup.
7. RAID 60 (6+0)
- Description: Combination of RAID 6 and RAID 0; RAID 6 arrays are striped.
- Advantages: High fault tolerance with better performance.
- Disadvantages: Requires at least eight disks, slower writes due to double parity.
8. RAID 1E (Enhanced Mirroring)
- Description: An extended RAID 1 that supports an odd number of disks.
- Advantages: Redundancy with better flexibility than RAID 1.
- Disadvantages: Limited adoption and slightly lower efficiency.
9. RAID 5E and RAID 6E (Enhanced RAID)
- Description: Variations of RAID 5 and RAID 6 that include a hot spare for quicker rebuilds.
- Advantages: Faster recovery after a disk failure.
- Disadvantages: Slightly reduced storage efficiency.
RAID levels along with minimum disks required, performance, storage utilization, data protection, and maximum disk failures it can sustain.
| RAID Level | Min. Disks Required | Performance | Storage Utilization | Data Protection | Max Disk Failures Supported |
|---|---|---|---|---|---|
| RAID 0 (Striping) | 2 | 🚀🚀🚀 (High) | 100% | ❌ No protection | 0 (Any disk failure = Data loss) |
| RAID 1 (Mirroring) | 2 | 🚀 (Moderate, Read: High, Write: Moderate) | 50% | ✅ Full copy of data on second disk | 1 |
| RAID 5 (Striping + Parity) | 3 | 🚀🚀 (Good Read, Moderate Write) | (N-1)/N | ✅ Can recover from single disk failure | 1 |
| RAID 6 (Striping + Double Parity) | 4 | 🚀 (Read: Good, Write: Slow due to dual parity) | (N-2)/N | ✅✅ Can recover from two disk failures | 2 |
| RAID 10 (1+0, Mirrored Striping) | 4 | 🚀🚀🚀 (Very High) | 50% | ✅ Can recover as long as one disk per mirrored pair survives | 1 disk per mirrored pair |
| RAID 50 (5+0, Striped RAID 5) | 6 | 🚀🚀 (Better than RAID 5) | (N-1)/N | ✅ Can recover from single disk failure per RAID 5 group | 1 per RAID 5 set |
| RAID 60 (6+0, Striped RAID 6) | 8 | 🚀 (Better than RAID 6) | (N-2)/N | ✅✅ Can recover from two disk failures per RAID 6 group | 2 per RAID 6 set |
| RAID 1E (Enhanced Mirroring) | 3 | 🚀 (Moderate, Read: High, Write: Moderate) | 50% | ✅ Can recover from single disk failure | 1 |
| RAID 5E (Enhanced RAID 5 with Hot Spare) | 4 | 🚀🚀 (Good Read, Moderate Write) | (N-2)/N | ✅ Hot spare allows faster rebuild | 1 |
| RAID 6E (Enhanced RAID 6 with Hot Spare) | 5 | 🚀 (Read: Good, Write: Slow) | (N-3)/N | ✅✅ Hot spare allows faster rebuild | 2 |
Key Terms:
- Performance: Higher 🚀 means better read/write speed.
- Storage Utilization: How much actual storage is available (e.g., RAID 5 with 4 disks = 75% utilization as one disk is used for parity).
- Data Protection: Indicates if RAID can recover from disk failures.
- Max Disk Failures Supported: How many disks can fail before data loss occurs.