RAID 10
RAID 10 Quick Facts
What Is RAID 10?
RAID 10, also called RAID 1+0, is created by forming mirrored drive pairs and then striping data across those mirror sets. Mirroring provides redundancy while striping allows multiple mirror groups to participate in I/O.
Unlike RAID 5 and RAID 6, RAID 10 does not rely on parity. That avoids parity calculations during normal writes and makes the layout attractive for workloads that prioritize predictable write performance, latency, and comparatively simple rebuilds.
Data Is Mirrored First and Striped Across Mirror Sets
A common four-drive RAID 10 layout contains two mirrored pairs. Data is striped across those two mirrors. Each mirror contains redundant copies of its portion of the striped data.
Simplified conceptual illustration of two mirrored pairs striped together.
RAID 10 Usable Capacity
In a conventional two-way mirrored RAID 10 layout, half of the raw drive capacity is used for mirrored copies. This produces approximately 50% nominal capacity efficiency when all participating drives are the same size.
Four 4 TB Drives
(4 ÷ 2) × 4 TB = 8 TB nominal RAID 10 capacity.
Eight 8 TB Drives
(8 ÷ 2) × 8 TB = 32 TB nominal RAID 10 capacity.
RAID 10 Can Survive Multiple Drive Failures
RAID 10 may survive more than one drive failure when those failures occur in different mirror pairs. Each affected pair must retain at least one surviving member for the complete striped data set to remain available.
Fault Tolerance Depends on Which Drives Fail
A RAID 10 array can fail if all members of the same mirror set are lost. For example, a four-drive RAID 10 may survive two drive failures in different mirror pairs, but two failures within the same pair can make the array unavailable.
Why RAID 10 Is Often Chosen for Performance-Sensitive Workloads
RAID 10 can distribute reads and writes across multiple mirror sets without parity calculations. This can provide strong random and sequential performance, particularly with multiple active mirror pairs.
Actual performance depends on the number and type of drives, controller or software implementation, queue depth, stripe size, workload, caching, host interface, filesystem, and application behavior. RAID 10 should not be assumed to scale perfectly with drive count.
RAID 10 Rebuilds Are Mirror-Based
When one member of a mirror pair fails, the replacement member can be rebuilt by copying data from the surviving mirror member. No parity reconstruction is required.
Simpler Does Not Mean Instant
RAID 10 rebuild duration still depends on drive size, throughput, controller behavior, workload activity, rebuild priority, system bandwidth, and storage media performance.
RAID 10 Strengths
- No parity calculations during normal writes.
- Strong read and write performance potential.
- Fast, straightforward mirror-based rebuild logic.
- Can survive multiple failures when they occur in different mirror pairs.
- Well suited to latency-sensitive and transactional workloads.
RAID 10 Limitations
- Typical two-way mirror layouts use only about 50% of raw capacity.
- Requires an even number of drives in common implementations.
- Fault tolerance depends on failure placement.
- Higher raw-drive cost per usable TB than many parity layouts.
- RAID 10 does not replace independent backups.
When RAID 10 May Be Appropriate
RAID 10 is commonly considered when performance, low write overhead, redundancy, and predictable recovery behavior are more important than maximizing usable capacity.
RAID 10 Compared With RAID 5 & RAID 6
| RAID Level | Technique | Typical Capacity | Fault Tolerance | Primary Tradeoff |
|---|---|---|---|---|
| RAID 5 | Single parity | (N − 1) × smallest drive | 1 drive | High efficiency with parity write overhead |
| RAID 6 | Dual parity | (N − 2) × smallest drive | 2 drives | More redundancy with greater parity overhead |
| RAID 10 | Mirrors + striping | Typically 50% | Topology-dependent | Strong performance with lower capacity efficiency |
Calculate Your RAID 10 Configuration
Use the Tech Supply Direct RAID Calculator to compare RAID 10 capacity, storage efficiency, fault tolerance, estimated performance, hot-spare impact, and hardware cost.
RAID 10 FAQ
How many drives are required for RAID 10?
A conventional RAID 10 requires at least four drives and is commonly built with an even number of members.
How much capacity does RAID 10 provide?
A standard two-way mirrored RAID 10 typically provides approximately 50% of the raw drive capacity.
How many drives can RAID 10 lose?
It depends on which drives fail. Multiple failures can be tolerated if every mirror pair retains at least one member.
Is RAID 10 faster than RAID 6?
RAID 10 often has less write overhead because it does not maintain parity, but actual performance depends on drive type, controller, workload, cache, and implementation.
Is RAID 10 the same as RAID 1?
No. RAID 1 is a mirror. RAID 10 combines multiple mirror sets and stripes data across them.
Is RAID 10 a backup?
No. RAID 10 protects against certain drive failures but does not replace an independent backup strategy.
RAID 10 Redundancy Is Not a Backup
Mirroring protects against certain member-drive failures, but it does not protect against accidental deletion, data corruption, ransomware, application errors, catastrophic system loss, or every other form of data loss. Important data should also be protected with independent, tested backups.