Storage RAID Calculator
Calculate RAID capacity and performance instantly. Get usable space, efficiency, fault tolerance, and speed metrics for RAID 0, 1, 5, 6, 10, 50, and 60 configurations.
Free RAID Calculator: Calculate Storage Capacity & Performance Online
Calculate RAID array capacity, usable storage, fault tolerance, and performance metrics instantly for RAID 0, 1, 5, 6, 10, 50, and 60 configurations. Plan your server storage, NAS setup, or enterprise data center with accurate RAID calculations and efficiency ratings.
What Is a RAID Calculator (And Why You Need One)?
A RAID calculator is a tool that computes usable storage capacity, performance characteristics, and fault tolerance for Redundant Array of Independent Disks (RAID) configurations. RAID combines multiple physical drives into a single logical unit to improve performance, redundancy, or both—but calculating exact usable capacity requires complex formulas that vary by RAID level. According to SNIA's Storage Networking Primer, proper RAID planning prevents costly over-provisioning and under-capacity issues.
Professional RAID calculators go beyond simple capacity math. They calculate parity overhead, stripe size efficiency, read/write performance multipliers, rebuild time estimates, and failure probability—helping you choose the optimal RAID level for your workload. Whether you're building a home NAS with 4 drives or planning a 100-disk enterprise storage array, accurate RAID calculations ensure you get the capacity and performance you paid for.
Why RAID Calculators Are Essential for Storage Planning:
Accurate Capacity Planning
- • Avoid surprises: Know exact usable capacity before purchasing drives
- • Budget correctly: Calculate how many drives you actually need
- • Plan growth: Understand capacity for future expansion
- • Prevent waste: Don't over-provision expensive enterprise drives
Performance Optimization
- • Match workloads: Choose RAID level for your read/write patterns
- • Calculate IOPS: Estimate input/output operations per second
- • Balance speed vs safety: Compare performance vs redundancy trade-offs
- • Optimize costs: Get best performance per dollar spent
Real RAID Capacity Examples
Raw capacity: 16TB
Usable capacity: 12TB (75% efficiency)
Lost to parity: 4TB (1 drive) Can survive 1 drive failureRaw capacity: 16TB
Usable capacity: 8TB (50% efficiency)
Lost to mirroring: 8TB (half) Fast performance, can survive multiple failuresRaw capacity: 48TB
Usable capacity: 32TB (66.7% efficiency)
Lost to parity: 16TB (2 drives) Can survive 2 simultaneous drive failuresRaw capacity: 3TB
Usable capacity: 3TB (100% efficiency)
Lost to redundancy: 0TB ⚠️ No fault tolerance - any drive failure loses all dataHow to Calculate RAID Capacity in 3 Easy Steps
đź’ˇ Pro Tip: Use Quick Presets for Common Scenarios
Skip manual configuration with our quick presets: Home NAS (RAID 5 with 4Ă—4TB drives for 12TB usable storage), Gaming Rig (RAID 0 with 2Ă—2TB SSDs for 4TB maximum speed), Enterprise (RAID 10 with 8Ă—2TB drives for balanced performance), or Max Safety (RAID 6 with 6Ă—4TB drives for 16TB with dual-drive fault tolerance). These presets represent the most popular real-world configurations used by IT professionals and storage enthusiasts.
7 RAID Levels: Complete Comparison Guide
Data is split across all drives for maximum performance and capacity. All drive space is usable (100% efficiency). Zero fault tolerance—if any single drive fails, you lose everything. Best for temporary storage, video editing scratch disks, or situations where speed matters more than data safety. Read/write speeds multiply by number of drives. Minimum 2 drives required. Popular for gaming PCs with dual NVMe SSDs.
Data is duplicated across all drives—every drive contains an identical copy. Only 50% capacity is usable (one drive's worth), but you get maximum redundancy. Can survive all drives failing except one. Excellent read performance (reads from all drives), standard write performance (must write to all drives). Minimum 2 drives required. Perfect for critical data that must never be lost, like operating system drives or important documents. See RAID 1 technical details.
Data and parity information are distributed across all drives. One drive's worth of capacity is used for parity (so 4×4TB = 12TB usable). Can survive 1 drive failure—the array continues operating and data can be rebuilt. Good balance between capacity, performance, and redundancy. Minimum 3 drives required. Most popular RAID level for home NAS and small business servers. Write performance is slower than RAID 0/10 due to parity calculation overhead. Rebuild times increase significantly with larger drives (8TB+ drives take 24-48 hours to rebuild).
Like RAID 5 but with two parity drives worth of data (so 6×4TB = 16TB usable). Can survive 2 simultaneous drive failures—critical for large arrays where rebuild times are long. If a drive fails during RAID 5 rebuild, you lose everything; RAID 6 prevents this scenario. Minimum 4 drives required. Write performance is slower than RAID 5 due to double parity calculation. Recommended for arrays with drives larger than 4TB, or any mission-critical data that requires extra protection. Enterprise standard for multi-TB storage systems.
Combines RAID 1 mirroring and RAID 0 striping—data is mirrored in pairs, then striped across pairs. 50% usable capacity (like RAID 1), but with excellent read AND write performance (like RAID 0). Can survive multiple drive failures as long as you don't lose both drives in a mirror pair. Minimum 4 drives required (must be even number). Rebuilds are faster than RAID 5/6 because you're just copying data, not recalculating parity. Industry standard for database servers, virtualization hosts, and high-performance applications. More expensive per TB than RAID 5/6 but worth it for I/O-intensive workloads.
Multiple RAID 5 arrays striped together for better performance than single RAID 5. Typically configured as two RAID 5 sets of 3+ drives each, striped at the top level. Better write performance than RAID 5, faster rebuilds (only rebuild one RAID 5 set), and can survive 1 drive failure per RAID 5 set. Minimum 6 drives required. More expensive than RAID 5 but provides performance boost for write-heavy workloads. Used in mid-sized enterprise storage where RAID 5 performance is insufficient but RAID 10's 50% capacity loss is too expensive.
Multiple RAID 6 arrays striped together for maximum enterprise-grade redundancy. Like RAID 50 but with double parity in each set—can survive 2 drive failures per RAID 6 set. Minimum 8 drives required (typically configured as two RAID 6 sets of 4+ drives). Provides RAID 6 safety with better performance and faster rebuilds. The most fault-tolerant nested RAID level available. Used in critical enterprise storage systems, datacenters, and applications where data loss is absolutely unacceptable. Higher capacity cost than RAID 6 due to striping overhead.
10 Real-World RAID Calculator Scenarios
1. Home NAS Setup Planning
Calculate capacity for home network-attached storage before buying drives. Most home users choose RAID 5 with 4Ă—4TB drives (12TB usable) for family photos, videos, and backups. Use our calculator to compare RAID 1 (8TB usable, max safety) vs RAID 5 (12TB usable, balanced) vs RAID 0 (16TB usable, no protection) to match your budget and safety requirements. Popular NAS brands like Synology and QNAP support all standard RAID levels.
2. Video Editing Workstation Storage
Video editors need fast storage for 4K/8K footage. Calculate RAID 0 with 2-4 NVMe SSDs for maximum sequential read/write speeds (critical for real-time 4K timeline playback). While RAID 0 has no redundancy, editors typically work with footage copies and archive to separate redundant storage after projects complete. Our PSU calculator helps ensure your power supply can handle multiple high-power NVMe drives.
3. Small Business File Server
Plan storage for company file shares, user home directories, and shared drives. RAID 6 with 6×4TB drives (16TB usable) provides dual-drive fault tolerance—critical for business data. Calculate rebuild times to ensure array survives second drive failure during long rebuild periods. Budget-conscious businesses may use RAID 5, but RAID 6 is recommended for drives larger than 2TB due to higher rebuild failure risk during lengthy rebuilds (24-48 hours for 4TB+ drives).
4. Database Server Configuration
Databases need fast random I/O for queries and transactions. RAID 10 with 8Ă—2TB enterprise SSDs (8TB usable) provides excellent read/write performance with redundancy. Calculate exact capacity needed for database data files, transaction logs, and temp databases. RAID 10's 50% capacity overhead is justified by superior performance for OLTP workloads. Consider our general calculator for IOPS and throughput planning.
5. Gaming PC Storage Optimization
Gamers want fast load times without spending thousands on SSDs. Calculate RAID 0 with 2×1TB NVMe SSDs (2TB usable) for game installations, delivering near-linear speed improvements for large open-world games. Keep OS and saves on separate single SSD for safety—RAID 0 game library can be re-downloaded if drive fails. Check our bottleneck calculator to ensure your GPU and CPU can utilize RAID 0 speeds.
6. Enterprise Data Center Planning
Calculate capacity for SAN (Storage Area Network) and large-scale storage systems. RAID 60 with 16×8TB drives (80TB+ usable) provides maximum redundancy for petabyte-scale deployments. Ensure proper capacity planning to avoid expensive emergency drive purchases. Enterprise RAID controllers support hot spares and background verification—factor these into total drive count calculations.
7. Media Server and Plex Libraries
Calculate storage for movie and TV show collections. RAID 5 with 4×8TB drives (24TB usable) gives plenty of space for 4K media libraries while maintaining fault tolerance. Plex media streaming doesn't require RAID 10 speeds—RAID 5 provides adequate sequential read performance for multiple simultaneous streams at lower cost per TB. Budget extra capacity for growing libraries (many users fill 24TB within 2-3 years).
8. Photography and RAW File Storage
Professional photographers need safe storage for irreplaceable RAW files. RAID 1 with 2×4TB drives (4TB usable) provides complete redundancy— if one drive fails, your photos are safe on the other. Calculate total capacity needed based on camera RAW file size and shooting volume (50MP RAW files are 50-80MB each, so 4TB holds ~50,000-80,000 photos). Many pros use RAID 1 for current work, then archive to separate drives.
9. Virtual Machine Host Storage
Virtualization hosts (VMware ESXi, Proxmox, Hyper-V) need fast storage for multiple VMs. RAID 10 with 6Ă—1TB SSDs (3TB usable) provides excellent random I/O for virtual disk operations. Calculate capacity for VM disk files, snapshots, and ISO images. Each VM typically needs 20-100GB depending on OS and applications. Budget 20% extra for snapshot overhead and thin provisioning over-commitment.
10. Backup Server Capacity Planning
Backup servers prioritize capacity over speed. RAID 6 with 8Ă—12TB drives (72TB usable) provides massive storage for backup retention with dual-drive fault tolerance. Calculate total capacity for full backups plus incremental chains (many organizations keep 30-90 days of backups). Since backups are sequential writes, RAID 6 write penalty is acceptable. Always plan 20-30% extra capacity for backup growth over 3-year drive lifecycle.
8 RAID Calculation Mistakes That Waste Money
1. Assuming 100% Usable Capacity on All RAID Types
Only RAID 0 gives 100% usable capacity. RAID 1 wastes 50%, RAID 5 loses 1 drive, RAID 6 loses 2 drives, RAID 10 loses 50%. Buying 20TB of raw drives thinking you'll get 20TB usable in RAID 5 leaves you with only 15TB—a costly surprise. Always calculate before purchasing drives to avoid under-provisioning.
2. Using RAID 5 with Large Drives (8TB+)
RAID 5 rebuild times increase exponentially with drive size. An 8TB drive takes 24-48 hours to rebuild, during which time a second drive failure destroys the array. Industry experts recommend RAID 6 for drives over 4TB due to higher failure probability during long rebuilds. The extra cost of 1 additional parity drive is far less than total data loss.
3. Mixing Different Drive Sizes in RAID Arrays
RAID arrays use the smallest drive's capacity for all drives. Mixing a 4TB drive with 3Ă—8TB drives in RAID 5 gives you only 12TB usable (4 drives Ă— 3TB smallest minus 1 for parity), wasting 15TB. Always use identical drive models and capacities in RAID arrays. Save mismatched drives for separate non-RAID storage or hot spares.
4. Choosing RAID Level Based on Capacity Alone
RAID 0 gives maximum capacity but zero safety—any drive failure loses everything. Choosing RAID 0 for important data to maximize capacity is false economy. Match RAID level to data criticality: RAID 0 for temp/cache, RAID 1 for critical data, RAID 5/6 for general storage, RAID 10 for databases. Calculate capacity AND evaluate fault tolerance requirements.
5. Forgetting to Account for Hot Spare Capacity
Enterprise RAID arrays should include 1-2 hot spare drives for automatic rebuilds. If you calculate exactly 16TB usable from 4Ă—4TB RAID 5, you have no spare for immediate rebuild. Add 1 extra drive as hot spare (5 total) so rebuilds start automatically when a drive fails, minimizing vulnerability window. Hot spares don't increase usable capacity but dramatically improve reliability.
6. Not Planning for Filesystem Overhead
Filesystems (NTFS, ext4, XFS, BTRFS) consume 1-5% of RAID capacity for metadata. A perfectly calculated 12TB RAID 5 array yields only 11.4-11.8TB actual usable space after formatting. Budget extra capacity for filesystem overhead, especially on smaller arrays where percentage impact is higher. Also reserve 10-15% free space for optimal filesystem performance.
7. Using RAID as a Backup Solution
RAID is NOT backup—it only protects against drive failure, not deletion, corruption, ransomware, fire, or theft. Calculate separate backup storage in addition to RAID arrays. Follow 3-2-1 backup rule: 3 copies of data, 2 different media types, 1 offsite copy. RAID keeps your data available during hardware failures; backups keep your data safe from everything else. Budget for both RAID and backup storage separately.
8. Ignoring RAID Controller Cache and Features
Hardware RAID controllers with cache (512MB-8GB) dramatically improve RAID 5/6 write performance. Software RAID saves money but uses CPU cycles and has no write cache. When calculating performance, factor in controller type. Enterprise workloads benefit from hardware RAID with battery-backed cache; home users can use software RAID (mdadm, Windows Storage Spaces, ZFS) to save costs.
Frequently Asked Questions About RAID
What is the best RAID level for a home NAS?
RAID 5 is the most popular choice for home NAS with 4-6 drives, providing good balance between capacity (75-83% usable), redundancy (1 drive failure tolerance), and cost. For 2-drive NAS, use RAID 1 (50% capacity, max safety). For critical data or drives larger than 4TB, consider RAID 6 for dual-drive failure protection. Avoid RAID 0 unless speed matters more than data safety.
How much usable capacity do I get from RAID 5 with 4Ă—4TB drives?
12TB usable capacity (75% efficiency). RAID 5 uses one drive's worth of capacity for parity, so the formula is (n-1) Ă— drive_size = (4-1) Ă— 4TB = 12TB. The parity drive is distributed across all drives (not a dedicated drive), allowing the array to survive any single drive failure. After filesystem formatting, expect 11.4-11.8TB actual available space.
Is RAID 0 safe for any data?
RAID 0 is safe only for temporary or easily-replaceable data like video editing scratch disks, game installations, download caches, or rendering temp files. If ANY drive in RAID 0 fails, you lose 100% of data across all drives—there's zero fault tolerance. Never use RAID 0 for irreplaceable files, photos, documents, or critical business data. Think of RAID 0 as "fast storage" not "safe storage."
Why is RAID 10 better than RAID 5 for databases?
RAID 10 provides superior write performance critical for database transaction logs and OLTP workloads. Databases perform many small random writes—RAID 5 has significant write penalty due to parity calculation (requires read-modify-write cycles for each update). RAID 10 simply mirrors writes with no parity overhead, delivering 2-4× better write IOPS than RAID 5. The 50% capacity cost is justified by performance gains and faster rebuild times. See database RAID benchmarks for detailed comparisons.
Can I add more drives to an existing RAID array?
It depends on your RAID controller/software. Some modern controllers support online capacity expansion—you can add drives to RAID 5/6 arrays and the system automatically redistributes data. Synology, QNAP, and enterprise controllers support this. However, many basic RAID controllers and older systems require backing up data, recreating the array with more drives, and restoring. Always check your RAID controller documentation before attempting expansion. Software RAID (mdadm, ZFS) often supports online expansion.
What happens during a RAID 5 rebuild if another drive fails?
You lose all data—RAID 5 can only survive 1 drive failure. During rebuilds (which take 6-48 hours depending on drive size), the array operates in degraded mode with zero fault tolerance. If a second drive fails during this window, the array fails completely. This is why RAID 6 is recommended for larger drives—it survives 2 failures, protecting you during long rebuild periods. Always monitor RAID arrays and replace failed drives immediately to minimize vulnerability. Use our monitoring tools for drive health tracking.
Should I use hardware or software RAID?
Hardware RAID with battery-backed cache for enterprise/business (better performance, protected write cache, CPU offload); software RAID for home/budget builds (free, flexible, modern features like ZFS/BTRFS). Hardware RAID cards cost $200-$2000+ but deliver consistent performance and reliability. Software RAID uses CPU cycles but modern CPUs handle this easily. ZFS (TrueNAS) and BTRFS offer advanced features like snapshots and bit-rot protection that hardware RAID lacks. For critical workloads, invest in hardware RAID with cache.
How long does a RAID rebuild take?
Rebuild time depends on drive size, RAID controller speed, and array activity: 1TB drive: 2-4 hours, 4TB drive: 8-12 hours, 8TB drive: 24-48 hours, 12TB+ drive: 48-72 hours. Rebuilds run slower under load (30-50% slower if array is actively serving files). Enterprise controllers with dedicated processors rebuild faster than software RAID. Large drives (8TB+) have worryingly long rebuild windows—another reason to use RAID 6 instead of RAID 5 for big drives. Plan maintenance windows for rebuilds in production environments.
Advanced RAID Planning Strategies
Capacity Planning for Growth
Calculate RAID capacity with 3-year growth in mind. Data expands 40-60% annually for most organizations. If you need 10TB today, budget for 20-25TB capacity to avoid expensive mid-lifecycle expansions. Larger initial arrays are more cost-effective per TB than incremental additions. Consider future drive availability—buying identical drives 2 years later may be impossible.
Hot Spare Configuration
Configure 1 hot spare per 8-12 drives in enterprise arrays for automatic rebuilds. Hot spares reduce rebuild window from "when you notice + order + ship + install + rebuild" (days/weeks) to "automatic immediate rebuild" (hours). Calculate hot spare costs into total drive budget—they don't increase capacity but dramatically improve uptime. Shared hot spares can serve multiple RAID arrays.
Performance-Capacity Trade-off Analysis
Compare RAID 5 vs RAID 10 with actual numbers: 8Ă—2TB RAID 5 = 14TB usable, good performance. 8Ă—2TB RAID 10 = 8TB usable, excellent performance. If your workload is I/O-intensive (databases, VMs), the 43% capacity loss for 2-4Ă— performance gain may be worthwhile. Calculate cost per IOPS, not just cost per TB, for performance-critical applications.
Mixed RAID Tier Architecture
Use multiple RAID levels in tiered storage: RAID 10 with SSDs for databases and hot data (fast, expensive), RAID 6 with HDDs for file storage (balanced), RAID 5 with large HDDs for archives (cheap per TB). Calculate capacity needs per tier based on data temperature. This optimizes cost vs performance vs capacity across your entire storage infrastructure.
Rebuild Time Risk Assessment
Calculate URE (Unrecoverable Read Error) risk during rebuilds. Consumer drives have 1 URE per 10^14 bits read. Reading 12TB during rebuild has ~10% chance of hitting URE, which fails RAID 5 rebuilds. Enterprise drives (10^15-10^17 URE rate) reduce this risk 10-100Ă—. For large arrays with consumer drives, RAID 6's double parity protects against URE-induced rebuild failures. Budget for enterprise drives or use RAID 6.
Stripe Size Optimization
Adjust RAID stripe size (chunk size) based on workload: 64KB for databases (matches typical I/O size), 128-256KB for file servers, 512KB-1MB for video streaming. Default 64KB works well generally, but tuning can improve performance 20-40% for specific workloads. Calculate optimal stripe size: make it match or be multiple of your application's typical I/O pattern for best alignment.
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