1. What is RAID With Hot Spare?

A RAID configuration with hot spare includes one or more standby drives that automatically replace failed drives. This provides additional fault tolerance beyond the standard RAID parity protection.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( disks \) — Total number of disks in the array
• \( parity \) — Number of parity disks (depends on RAID level)
• \( size \) — Size of each disk in GB
• 1 — Represents the hot spare disk

Explanation: The formula calculates usable storage by subtracting parity disks and hot spare from total disks, then multiplying by individual disk size.

3. Importance of Hot Spare Calculation

Details: Proper capacity planning with hot spares ensures you have both adequate storage space and redundancy. Hot spares reduce downtime when disks fail but reduce available capacity.

4. Using the Calculator

Tips: Enter total disks (minimum 2), parity disks (minimum 1), and disk size in GB. For RAID 5, parity is 1. For RAID 6, parity is 2. The hot spare is automatically accounted for.

5. Frequently Asked Questions (FAQ)

Q1: What RAID levels support hot spares?
A: All RAID levels (1, 5, 6, 10, etc.) can use hot spares, though the benefit is greatest with parity-based RAID (5/6).

Q2: How many hot spares should I have?
A: Typically 1-2 hot spares per array, or 1 per 30 disks in large systems. More spares increase protection but reduce capacity.

Q3: Does the hot spare need to be same size as other disks?
A: Yes, ideally identical in size and preferably same model to ensure compatibility during rebuild.

Q4: What's the difference between hot and cold spare?
A: Hot spare is powered on and automatically used. Cold spare must be manually installed when needed.

Q5: When should I use a hot spare?
A: In mission-critical systems where minimizing downtime is essential, or when physical access to replace disks is difficult.