RAID 10, also known as RAID 1+0, is a hybrid RAID configuration that combines disk mirroring and disk striping to protect data and improve performance. Choosing the best RAID 10 settings requires balancing protection, performance, and storage capacity. The most important considerations are RAID 10 block size, stripe size, number of disks, and disk types.
What is RAID 10?
RAID 10 uses four or more identical drives and “mirrors” two drives to create a RAID 1 array, then “stripes” the RAID 1 arrays together using block-level striping. This results in a RAID 0 array made up of mirrored drives. RAID 10 provides fault tolerance and improved performance compared to a single drive or RAID 0 alone. If one drive in the RAID 10 array fails, the mirrored drive ensures continued access to data. RAID 10 is best suited for applications requiring high performance and reliability, such as database servers and virtual machine hosts.
Key Factors in RAID 10 Configuration
There are four key factors to consider when configuring RAID 10:
- Block size
- Stripe size
- Number of disks
- Disk types
Adjusting these factors allows tuning RAID 10 for an ideal balance of performance, protection, and storage capacity.
Block Size
Block size, also called chunk size, controls how data is written to disk in segments. A smaller block size reduces the chance of data loss in the event of drive failure. Typical block sizes are 8KB, 16KB, 32KB, and 64KB. Most operating systems and RAID controllers default to a 64KB or 128KB block size. However, database and virtualization workloads perform better with a smaller block size like 8KB or 16KB. This minimizes wasted space when writing smaller files or database records.
Stripe Size
Stripe size controls how data is striped across the RAID 10 array. Larger stripe sizes improve performance for sequential reads and writes. Typical stripe sizes range from 64KB to 1024KB (1MB). Matching the stripe size to the block size allows optimized performance. For random workloads like databases, a smaller stripe size of 64KB to 128KB works best.
Number of Disks
RAID 10 requires a minimum of four disks, but more disks can increase capacity and performance. For most implementations, six to eight disks hits the best balance between performance, capacity, and cost. Going above eight disks increases rebuild times and risk of multiple disk failures during rebuilds.
Disk Types
RAID 10 can use different types of disks – high RPM SAS and SATA drives, SSDs, or a mix. Using all SSDs offers the highest performance. A hybrid RAID 10 configuration with SSDs for caching and high capacity HDDs for storage can provide a cost-effective balance.
RAID 10 Use Cases
RAID 10 works well for these key use cases:
- Database servers – Provides low latency and high IOPS for heavy transactional workloads
- Virtualization and VDI environments – Minimizes latency for optimal VM performance
- Mail servers and web servers – Improves reliability and sustains performance under heavy workloads
- High performance computing – Low latency access to data for real-time analysis
RAID 10 vs RAID 01
RAID 10 is sometimes confused with RAID 01, but they are implemented differently:
- RAID 10 – Stripes first then mirrors
- RAID 01 – Mirrors first then stripes
Both provide the same level of redundancy. RAID 10 performs better for random writes while RAID 01 optimizes large sequential workloads. For most uses, RAID 10 is preferable.
RAID 10 Configuration Guidelines
Follow these guidelines when configuring RAID 10:
- Use a minimum of 4 and maximum of 8 disks
- SSDs provide the best performance, or use a SSD cache pool
- Match the stripe size to the operating system’s default block size
- Use a smaller block size for database workloads – 8KB or 16KB
- Keep all drives identical for optimal performance
- Add hot spares to allow rebuilds during failures
RAID 10 Setup Steps
Follow these steps to configure RAID 10 on a typical server:
- Install drives into the server and connect power and data cables
- Enter the RAID configuration utility during server boot (Ctrl+R, Ctrl+I, etc)
- Select the disks to include in the RAID 10 array
- Choose RAID 10 and configure the stripe size/block size
- Initialize the RAID 10 array and verify status
- Install the operating system and configure as necessary
- Test performance with disk benchmark tools
Monitoring and Maintaining RAID 10
Best practices for ongoing RAID 10 monitoring and maintenance:
- Check RAID status weekly and verify synchronization
- Monitor drive health using S.M.A.R.T. tools
- Perform regular surface scans to identify bad sectors
- Schedule a scrubbing to check data integrity quarterly
- Monitor drive temperatures and chassis airflow
- Replace failed drives immediately per the vendor’s instructions
- Consider scheduled preventative drive replacements every 3-5 years
Advantages of RAID 10
Key advantages of using RAID 10 include:
- Very high read and write performance – ideal for transactional workloads
- Disk failure does not interrupt access to data due to mirroring
- Up to 50% storage efficiency
- Tunable for optimal performance based on workload
- Ability to recover from multiple drive failures
- Can utilize SSDs for maximum speed
Disadvantages of RAID 10
Potential disadvantages of RAID 10 to consider:
- Higher cost than RAID 5 or 6 due to more physical disks
- Rebuild times increase significantly as more drives are added
- Requires a minimum of 4 drives
- Half the total capacity is lost to redundancy/mirroring
- Does not ensure data integrity like RAID 5 or 6
- More complex to configure vs basic mirroring or parity-based RAID
RAID 10 Performance
RAID 10 provides excellent performance for both reads and writes. By striping I/O across mirrored disks, RAID 10 can achieve data transfer speeds meeting or exceeding a single disk. Using SSDs further improves throughput and IOPS. Here are sample RAID 10 performance benchmarks:
| RAID 10 Configuration | Reads | Writes |
| 4 x 10K HDD RAID 10 | 400 MB/s | 350 MB/s |
| 4 x SSD RAID 10 | 850 MB/s | 680 MB/s |
| 8 x 15K HDD RAID 10 | 680 MB/s | 620 MB/s |
As shown, RAID 10 provides substantial performance gains compared to a single disk. Scaling up to 8 disks and using SSDs boosts throughput and IOPS for the most demanding workloads.
RAID 10 Storage Capacity
RAID 10 capacity is a tradeoff for performance and redundancy. With RAID 10, the total usable capacity equals the size of the smallest disk times the number of disk pairs. For example, four 2 TB drives would result in 4 TB of usable RAID 10 storage. The capacity efficiency of RAID 10 is 50%.
If increased capacity is needed, options include:
- Add more drives to the RAID 10 array
- Use higher capacity drives
- Allocate a separate RAID 5, RAID 6, or JBOD array for storage capacity
RAID 10 Reliability
RAID 10 provides good protection against disk drive failure. Because drives are mirrored, a single disk failure will not result in data loss or downtime. RAID 10 can sustain multiple drive losses as long as no more than one failure occurs per mirrored pair. Rebuilding failed drives is also quicker than RAID 5 or 6 rebuilds.
However, RAID 10 does not provide the data integrity that RAID 5 or 6 offers. Silent data corruption can still occur. To protect against data corruption, add file system checksums or ZFS/Btrfs data integrity checking.
Conclusion
Optimizing RAID 10 comes down to tailoring the configuration for your specific workload and performance needs. Typical starting recommendations are:
- 4-8 drives for the array
- 64KB stripe size
- 16KB block size for databases
- Match disk types/speeds for best performance
From there, tuning block size, adding SSD caches, and adjusting the number of drives can further enhance performance and capacity. RAID 10 requires more drives than RAID 5 or 6, but offers higher speed for transactional and virtualized workloads. Carefully weighing these factors allows designing a RAID 10 implementation that fits your environment.
