RAID Performance Calculator

Analyze sequential speed, random IOPS, parity penalties, cache gains, rebuild stress, and latency with inputs. Plan balanced arrays for resilience, capacity, and realistic workloads.

Enter Array and Workload Inputs

RAID level

Number of disks

Disk size

Sequential read per disk (MB/s)

Sequential write per disk (MB/s)

Random read per disk (IOPS)

Random write per disk (IOPS)

Read ratio (%)

Application block size (KB)

Stripe size (KB)

Controller overhead (%)

Read cache hit rate (%)

Write cache contribution (%)

Queue depth efficiency (%)

Rebuild penalty (%)

Base latency per disk (ms)

The calculator estimates practical array behavior by combining disk capability, RAID write penalties, caching effects, queue efficiency, and rebuild stress.

Example Data Table

Scenario	RAID	Disks	Per-Disk Read	Per-Disk Write	Read Ratio
Virtualization host	RAID 10	8	550 MB/s	510 MB/s	65%
Backup repository	RAID 6	10	240 MB/s	220 MB/s	80%
Database volume	RAID 5	6	220 MB/s	210 MB/s	70%

Formula Used

Usable Capacity = Disk Size × Capacity Disks Allowed By RAID Level

Sequential Read = Per-Disk Read × Disk Count × Stripe Factor × Cache Read Boost × Queue Efficiency × Overhead Factor

Sequential Write = Per-Disk Write × Usable Data Disks × Stripe Factor × Cache Write Boost × Queue Efficiency × Overhead Factor × Rebuild Factor

Random Read IOPS = Per-Disk Read IOPS × Disk Count × Cache Effect × Queue Efficiency × Overhead Factor

Random Write IOPS = Per-Disk Write IOPS × Usable Data Disks ÷ RAID Write Penalty × Cache Effect × Queue Efficiency × Overhead Factor × Rebuild Factor

Estimated Latency = Base Latency × Latency Penalty ÷ Cache Relief Factor

Write penalty defaults are modeled as 1 for RAID 0, 1, and 10, 4 for RAID 5, and 6 for RAID 6.

How to Use This Calculator

Select the RAID level that matches your storage design.
Enter disk quantity, disk size, and per-disk throughput values.
Provide random IOPS, read percentage, block size, and stripe size.
Adjust controller overhead, cache behavior, queue efficiency, and rebuild impact.
Press the calculation button to place the result above the form.
Review capacity, throughput, IOPS, latency, and penalty indicators.
Use the CSV or PDF buttons to export the result set.

FAQs

1. What does this calculator estimate?

It estimates usable capacity, sequential bandwidth, random IOPS, write penalties, latency, and rebuild impact for common RAID layouts under configurable workloads.

2. Why is RAID 5 write performance lower?

RAID 5 must read old data, read old parity, write new data, and write new parity. That extra parity work reduces effective small-write performance.

3. Why does RAID 10 need an even disk count?

RAID 10 mirrors disks in pairs, then stripes across those pairs. An odd disk leaves one drive unmatched, so the layout becomes invalid.

4. Does cache always improve results?

No. Cache helps most when workloads reuse hot data or absorb bursts. Large streaming writes and cold random reads may see limited gains.

5. What is rebuild penalty?

It represents the performance loss while an array rebuilds or verifies data. During that period, controller and disk resources are partially consumed.

6. Should I match block size and stripe size?

Matching them thoughtfully helps. If block size aligns well with stripe geometry, the array performs fewer partial-stripe updates and writes more efficiently.

7. Are these numbers exact for every controller?

No. Vendors differ in firmware, cache policy, parity engines, queue handling, and background tasks. Use the output as an engineering estimate, not a benchmark guarantee.

8. Which RAID level is best for mixed workloads?

RAID 10 often performs best for mixed transactional workloads because it avoids parity penalties. RAID 6 offers stronger protection, but usually with slower writes.