RAID 50
RAID 50 Quick Facts
What Is RAID 50?
RAID 50, also called RAID 5+0, is a nested RAID layout. Multiple independent RAID 5 groups are created first, and data is then striped across those groups.
Each underlying RAID 5 group provides single-parity protection. The top-level stripe allows I/O to be distributed across multiple groups, which can increase aggregate performance compared with a single RAID 5 group of similar drive count.
Multiple RAID 5 Groups Are Striped Together
A minimum RAID 50 configuration can be formed from two three-drive RAID 5 groups. Each group can lose one member without failing. The top-level stripe spans both RAID 5 groups.
Simplified conceptual illustration of RAID 50.
RAID 50 Usable Capacity
Each RAID 5 group loses the equivalent capacity of one member drive to parity. The usable capacities of the RAID 5 groups are then combined by the top-level stripe.
Six 4 TB Drives
Two 3-drive RAID 5 groups: 2 × (3 − 1) × 4 TB = 16 TB nominal RAID 50 capacity.
Eight 8 TB Drives
Two 4-drive RAID 5 groups: 2 × (4 − 1) × 8 TB = 48 TB nominal RAID 50 capacity.
RAID 50 Can Survive Multiple Drive Failures
RAID 50 can survive more than one member-drive failure if no underlying RAID 5 group loses more than one member. For example, one failed drive in each of two separate RAID 5 groups can be tolerated.
Failure Placement Matters
If two drives fail within the same underlying RAID 5 group before that group's redundancy is restored, that RAID 5 group can fail and the entire RAID 50 virtual disk can become unavailable.
Why RAID 50 Can Outperform One Large RAID 5 Set
RAID 50 distributes I/O across multiple RAID 5 groups. This can increase aggregate throughput and create more parallelism than a single RAID 5 group, particularly when several groups are active simultaneously.
Each underlying RAID 5 group still maintains single parity, so parity-related write overhead remains. Actual performance depends on the number of groups, drives per group, media type, controller, cache, stripe size, queue depth, interface bandwidth, and workload.
RAID 50 Rebuilds Occur Within the Affected Group
When one drive fails, its underlying RAID 5 group reconstructs the missing data using that group's surviving data and parity. Other RAID 5 groups do not need to recreate the failed member's contents.
Smaller Groups Can Limit the Rebuild Domain
Dividing an array into multiple RAID 5 groups means a rebuild is generally concentrated within the affected group rather than spanning one very large parity set. Real rebuild duration still depends on drive size, workload, controller behavior, and system performance.
RAID 50 Strengths
- Can provide higher aggregate performance than one large RAID 5 group.
- Can survive multiple failures when they occur in different RAID 5 groups.
- Maintains better capacity efficiency than conventional RAID 10 in many configurations.
- Creates smaller parity groups within a larger array.
- Useful for larger arrays requiring a balance of performance and capacity.
RAID 50 Limitations
- Each RAID 5 group can tolerate only one failed member.
- Two failures in the same group can cause array failure.
- Parity write overhead remains within each group.
- Requires more drives and planning than basic RAID 5.
- RAID 50 does not replace independent backups.
When RAID 50 May Be Appropriate
RAID 50 is commonly considered for larger arrays where users want more parallelism than one RAID 5 set can provide while retaining relatively strong usable-capacity efficiency.
RAID 50 Compared With RAID 5, RAID 10 & RAID 60
| RAID Level | Architecture | Parity / Mirror Overhead | Fault Tolerance | Primary Tradeoff |
|---|---|---|---|---|
| RAID 5 | Single RAID 5 group | 1 drive equivalent | 1 drive | Simple, efficient single-parity array |
| RAID 10 | Striped mirrors | Typically 50% | Topology-dependent | Higher performance, lower capacity efficiency |
| RAID 50 | Striped RAID 5 groups | 1 drive equivalent per group | 1 drive per group | Capacity efficiency with group-level parallelism |
| RAID 60 | Striped RAID 6 groups | 2 drives equivalent per group | 2 drives per group | Greater resilience with additional parity overhead |
Calculate Your RAID 50 Configuration
Use the Tech Supply Direct RAID Calculator to compare RAID 50 capacity, storage efficiency, fault tolerance, estimated performance, hot-spare impact, and hardware cost.
RAID 50 FAQ
How many drives are required for RAID 50?
RAID 50 requires at least two RAID 5 groups. Because each RAID 5 group requires at least three drives, the practical minimum is six drives.
How many drives can RAID 50 lose?
It can lose one drive from each RAID 5 group simultaneously. Fault tolerance therefore depends on which groups contain the failed drives.
What happens if two drives fail in the same RAID 5 group?
That RAID 5 group can fail because single parity cannot reconstruct two missing member drives. Loss of one underlying group can cause the RAID 50 virtual disk to fail.
Is RAID 50 faster than RAID 5?
RAID 50 can provide more aggregate parallelism by striping across multiple RAID 5 groups, but actual performance depends on the hardware, group layout, workload, and controller implementation.
What is the difference between RAID 50 and RAID 60?
RAID 50 stripes across RAID 5 groups with single parity. RAID 60 stripes across RAID 6 groups with dual parity and therefore provides greater fault tolerance within each group.
Is RAID 50 a backup?
No. RAID 50 provides storage redundancy but does not replace an independent and tested backup strategy.
RAID 50 Redundancy Is Not a Backup
RAID 50 can protect against certain combinations of member-drive failures, but it does not protect against accidental deletion, corruption, ransomware, controller failure, catastrophic hardware loss, or every other source of data loss. Important data should still be protected with independent backups.