Rebuild time calculator

Rebuild Time Calculator: Control the Risk of RAID Double Failure

The moment a RAID disk fails is critical. The time it takes to rebuild onto a new spare disk is the most dangerous period for your data. If a second disk fails during this phase, data loss is guaranteed (except in RAID 6/Z2).

Our Reconstruction Time Calculator gives you a critical estimate in hours and minutes, allowing you to plan for risk windows and ensure the reliability of your infrastructure.

Why is Rebuild Time Crucial?

• Vulnerability Window (MTTR): The longer the rebuild takes, the higher the probability of a second failure (known as a “double failure”). This tool quantifies this risk.
• Disk Performance: Rebuild speed is limited by the sequential read throughput of the smaller capacity disk and not by the theoretical speed of the controller.
• Planning: Determine if you need faster spare drives (Hot Spares SSD or Fast Cold Spares HDD) to reduce this risk window.

How does the calculation work?

The calculation is simple yet powerful: it divides the capacity of the failed disk (in GB) by the effective read speed (in MB/s) of the other disks, applying a load factor to simulate system slowdown during the operation.

Enter your disk size, RAID level (for context), and your hardware’s read speed to get an accurate, quantifiable estimate. Plan for resilience, not failure.