When configuring a RAID array using solid state drives (SSDs), choosing the right RAID level is important for optimizing performance, capacity, and fault tolerance. SSDs have different characteristics than traditional hard disk drives (HDDs), so the standard guidance on RAID levels may not apply directly. The most popular RAID levels used with SSD arrays are RAID 0, RAID 1, RAID 5, RAID 6, and RAID 10. But which one is best for your needs? Here is a quick overview of key considerations when selecting a RAID level for SSDs:
Performance
RAID 0 offers the best performance since data is striped across all drives. There is no parity calculation overhead. RAID 10 also provides excellent performance through its mirrored stripe sets. RAID 5 and 6 have slower write speeds due to parity calculation on writes.
Capacity
RAID 0 offers full additive capacity of all drives. RAID 10 offers 50% of total capacity since it mirrors. RAID 5 and 6 have incremental capacity loss due to parity drives.
Fault tolerance
RAID 0 offers no fault tolerance. RAID 1, 5, 6, and 10 provide fault tolerance to drive failures, with RAID 6 offering the highest level of protection.
Cost
RAID 10 and 5/6 require more drives than RAID 0/1 for the same usable capacity. RAID 10 requires an even number of drives.
RAID 0
Overview
RAID 0 (also known as disk striping) spreads data evenly across two or more SSDs with no parity. RAID 0 provides high performance but no fault tolerance.
How RAID 0 Works
In RAID 0, logically sequential data is divided into fragments called “stripes” that get written across the SSDs in the array sequentially. This allows simultaneous reads/writes to the SSDs, improving overall speed. But if one SSD fails, all data in the array will be lost.
Benefits of RAID 0 SSDs
- Very high read/write performance – ideal for applications needing high IOPS
- Full capacity utilization of all drives
- Low cost to implement
Drawbacks of RAID 0 SSDs
- No fault tolerance – total data loss if one drive fails
- Potential loss of data with SSD write errors
- High disk I/O bottlenecks with multiple SSDs
Use Cases for RAID 0 SSDs
RAID 0 works well in these scenarios:
- Video editing/production servers needing high speed scratch disks
- High performance compute clusters without redundancy requirements
- Gaming PCs focused on max speed over data protection
Overall, RAID 0 SSD arrays provide the highest performance but no data protection. Use RAID 0 when speed is the top priority and data redundancy is not required.
RAID 1
Overview
RAID 1 (disk mirroring) creates an exact copy of data between two or more SSDs. It provides fault tolerance with good read speeds, but reduced capacity and slower writes.
How RAID 1 Works
RAID 1 duplicates all data from one SSD to another SSD in real-time. If one drive fails, the system can instantly switch to the mirrored drive without interrupting service. But total capacity is reduced to 50% with two mirrored drives.
Benefits of RAID 1 SSDs
- Excellent read performance – reads can be distributed across drives
- Simple fault tolerance with two drives
- Fast rebuild times if a drive fails
Drawbacks of RAID 1 SSDs
- 50% loss of total capacity
- Slower write performance due to data duplication
- Requires even number of SSDs
Use Cases for RAID 1 SSDs
RAID 1 is useful in these scenarios:
- Database servers needing good redundancy
- Critical systems where downtime must be avoided
- Smaller servers with limited drive bays
Overall, RAID 1 provides simple mirrored redundancy for improved fault tolerance using two SSDs. But the capacity loss may be prohibitive for larger arrays.
RAID 5
Overview
RAID 5 stripes data and parity information across 3 or more SSDs. It provides fault tolerance with good read speeds, but slower writes and reduced usable capacity compared to RAID 0.
How RAID 5 Works
Data is striped across all drives like RAID 0. Additional parity information is also calculated and written across the SSDs. If any single drive fails, the missing data can be recreated from the parity drive. But write performance suffers due to the parity calculation overhead.
Benefits of RAID 5 SSDs
- Good fault tolerance with 1 drive failure
- Strong read performance
- Efficient use of capacity
Drawbacks of RAID 5 SSDs
- Slow write speeds due to parity calculation
- Long rebuild times if drive fails
- Total failure if second drive dies before rebuild
Use Cases for RAID 5 SSDs
RAID 5 is well suited for:
- File and application servers needing redundancy
- Archival storage with more reads than writes
- Smaller arrays (3-4 drives) needing 1 drive fault tolerance
Overall, RAID 5 provides efficient redundancy for SSD arrays that are light on writes. But for busy databases or virtualized servers, the write penalty may be too high.
RAID 6
Overview
RAID 6 stripes data and dual parity information across 4 or more SSDs. It provides excellent fault tolerance but reduced performance and usable capacity compared to RAID 0/5.
How RAID 6 Works
RAID 6 is similar to RAID 5, but uses two independent parity blocks rather than one. This allows the array to survive the loss of any TWO drives. The cost is further reduced write performance and capacity.
Benefits of RAID 6 SSDs
- Excellent fault tolerance – can survive loss of 2 drives
- Useful for large arrays where rebuilds take longer
- Extra parity provides an additional safeguard
Drawbacks of RAID 6 SSDs
- Significantly slower write speeds due to dual parity
- Loss of usable capacity due to 2 parity drives
- Heavier resource demands on the storage controller
Use Cases for RAID 6 SSDs
RAID 6 works well for:
- Mission critical servers that cannot have downtime
- Large storage arrays (8+ drives) needing high fault tolerance
- Environments where drive replacement is difficult
Overall, RAID 6 provides excellent redundancy for write-heavy SSD workloads that demand high availability. But the performance/capacity tradeoffs may be overkill for smaller arrays.
RAID 10
Overview
RAID 10 combines mirrored sets of SSDs into a single striped array. It provides excellent performance plus redundancy, but at a higher cost.
How RAID 10 Works
RAID 10 creates a striped array whose members are mirrored drives. Data is duplicated on the mirrors, while reads/writes are load balanced across stripes. This provides fast I/O plus fault tolerance from the mirrors.
Benefits of RAID 10 SSDs
- Very high read and write throughput
- Full redundancy of mirrored drives
- Fast rebuilds if drive fails
Drawbacks of RAID 10 SSDs
- 50% loss of total capacity
- Higher hardware cost for drives
- Requires even number of SSDs
Use Cases for RAID 10 SSDs
RAID 10 excels in these scenarios:
- Database servers needing performance and redundancy
- Virtualized servers with heavy random I/O
- Mission critical applications requiring high availability
Overall, RAID 10 provides an excellent blend of speed, redundancy, and fast rebuilds for SSD arrays. But the drive cost and capacity limitations must be considered.
RAID Level Comparison
Here is a summary of key RAID level differences with SSDs:
| RAID Level | Fault Tolerance | Read Speed | Write Speed | Capacity Efficiency |
|---|---|---|---|---|
| RAID 0 | None | Excellent | Excellent | 100% |
| RAID 1 | Excellent | Excellent | Good | 50% |
| RAID 5 | Good | Excellent | Fair | 67% – 94% |
| RAID 6 | Excellent | Good | Poor | 50% – 88% |
| RAID 10 | Excellent | Excellent | Excellent | 50% |
Choosing the Right RAID Level for SSDs
So which RAID level is the best choice for your SSD array? Here are some general guidelines:
When to use RAID 0
Choose RAID 0 when:
- You need maximum disk performance for applications like video production/editing.
- Data redundancy is not required. The data is disposable or backed up.
- You have a reliable, backup power supply to avoid data loss from power failure.
RAID 0 works well for speed-dependent applications without redundancy requirements. Just be sure to regularly back up your data!
When to use RAID 1
Select RAID 1 when:
- Data redundancy and fast rebuilds are critical.
- You only need to safeguard against a single drive failure.
- Array capacity is less important than fault tolerance.
RAID 1 provides simple, cost-effective mirroring for small, critical SSD arrays.
When to use RAID 5
Choose RAID 5 for:
- General file and application servers needing good redundancy.
- Workloads focused more on reads than writes.
- Cost-effective redundancy in arrays with 3-4 SSDs.
RAID 5 hits a sweet spot between redundancy, capacity, and cost for lightly write-intensive SSD workloads.
When to use RAID 6
Select RAID 6 when:
- Uptime and data availability are absolutely critical.
- You have a busy, write-heavy workload.
- You need to protect against multiple drive failures.
Despite the performance tradeoffs, RAID 6 provides excellent fault tolerance for mission critical SSD arrays.
When to use RAID 10
Choose RAID 10 when:
- Maximum performance and fast rebuilds are top priorities.
- Cost is less important than speed, redundancy, and availability.
- You need an even blend of read and write performance.
For busy databases, virtual servers, or I/O heavy applications, RAID 10 is often the best choice despite the drive cost.
Optimizing RAID Performance with SSDs
To maximize the performance of your RAID SSD array, here are some additional tips:
Use enterprise SSDs
Consumer SSDs carry more risks of failures and slowdowns at high workloads. Enterprise SSDs have higher endurance ratings and performance consistency.
Enable SSD overprovisioning
This reserves extra spare area on each SSD to improve write performance and endurance.
Enable SSD TRIM support
The TRIM command helps SSDs garbage collect and maintain peak write performance.
Choose RAID controllers wisely
Select a RAID card optimized for SSDs, with features like caching, multi-threading, and fast I/O buses.
Consider M.2 NVMe drives
M.2 SSDs connect via PCIe instead of SATA for higher theoretical throughput.
Benchmark your workloads
Test your specific application workloads against different RAID levels to validate performance.
Monitor disk health
Keep a close eye on SSD wear levels, Smart stats, and disk errors to catch problems early.
Conclusion
Optimizing your RAID configuration requires a careful balance of performance, redundancy, and cost. For most write-heavy and mission critical workloads, RAID 10 provides an ideal blend of speed, fault tolerance, and availability for SSD arrays. But RAID 5 or 6 may provide more economical redundancy for light workloads. Matching your RAID level to the specific demands of your workload and business requirements is key to building a fast, reliable SSD storage solution.
