What is RAID 10?
RAID 10 is a storage technology that combines features of RAID 1 (mirroring) and RAID 0 (striping) to provide increased performance and reliability compared to a single drive (Definition of RAID 10). In a RAID 10 array, data is written in stripes across multiple drives and also duplicated on a second set of drives. This provides the performance benefits of RAID 0 striping along with the fault tolerance of RAID 1 mirroring.
Specifically, RAID 10 requires a minimum of 4 drives configured as 2 mirrored pairs (RAID 1). Data is striped across each mirrored pair, with a copy maintained on both drives. If one drive fails, its mirror still contains the data so there is no loss. RAID 10 provides extremely high I/O performance for both read and write operations while also protecting against a single drive failure.
Pros of Using RAID 10 for NAS
One of the biggest advantages of using RAID 10 for NAS is increased read and write performance. By striping data across multiple disks, RAID 10 allows for faster disk access and bandwidth (Enterprise Storage Forum). The performance is significantly better than using RAID 1 mirroring alone. RAID 10 can handle multiple simultaneous read and write requests, making it well-suited for busy NAS environments.
RAID 10 also provides better redundancy and fault tolerance compared to RAID 0 striping or RAID 1 mirroring alone (TechTarget). With RAID 10, data is mirrored and striped, so up to half the drives can fail without data loss. This makes it much more resilient than RAID 0. The dual-drive fault tolerance provides peace of mind for critical NAS data.
Overall, the combination of performance and redundancy makes RAID 10 a great choice for NAS systems that need both speed and protection against drive failures.
Cons of Using RAID 10 for NAS
One of the main drawbacks of using RAID 10 for a NAS is that it provides less total capacity compared to RAID 5 or RAID 6 configurations. Since RAID 10 requires mirroring, you lose 50% of the total drive capacity to redundancy. For example, four 2TB drives in RAID 10 would only provide 4TB of usable space, while RAID 5 would provide 6TB from the same four disks (source).
Another disadvantage of RAID 10 is that rebuilding the array after a disk failure takes longer compared to RAID 5 or RAID 6. With RAID 10, the rebuilding process involves both reading from the good disks and writing to the replacement disk. RAID 5 and 6 can rebuild more quickly since they only need to write parity data to the new disk (source).
Finally, RAID 10 is generally more expensive than RAID 5 or 6 because it requires a minimum of 4 drives. The greater number of disks needed makes both the upfront and ongoing costs higher for RAID 10. For budget-conscious home NAS builders, the lower costs of RAID 5 or 6 can be more appealing (source).
RAID 10 Performance
RAID 10 provides excellent performance for random read and write operations compared to other RAID levels. This is because with RAID 10, read and write operations occur in parallel across multiple drives [1]. Benchmarks show that RAID 10 can achieve over 200MB/s for random reads and writes.
Compared to RAID 5, RAID 10 offers significantly faster write speeds, often 4x as fast or more. This is because RAID 5 uses parity calculations that slow writes, while RAID 10 simply stripes and mirrors data across drives. One benchmark showed RAID 10 achieving over 1000 MB/s sequential writes, while RAID 5 only reached 225 MB/s [2].
RAID 10 also outperforms RAID 6 in most benchmarks, since RAID 6 uses two parity drives instead of one. One test showed RAID 10 averaging 615 MB/s reads and 593 MB/s writes, while RAID 6 managed 509 MB/s reads and 334 MB/s writes [3].
Overall, benchmarks demonstrate the clear performance advantage of RAID 10 over RAID 5 and RAID 6, especially for write operations.
RAID 10 Reliability
RAID 10 is considered one of the most reliable RAID configurations due to its use of mirroring. With RAID 10, each drive is mirrored by a second identical drive. If one drive in the mirrored pair fails, the system can instantly failover to the other drive without any disruption to operations [1]. This provides excellent protection against single drive failures.
In contrast, RAID levels like RAID 5 and RAID 6 rely on parity to recover from single drive failures. This means if a drive fails, the array has to rebuild the data on the new drive using calculations, which takes much longer than RAID 10’s instant mirror failover. However, RAID 6 can sustain up to two drive failures by using a second parity drive [2].
The mean time between failures (MTBF) rating for a RAID 10 array is equal to the MTBF rating of a single drive divided by the number of drive pairs. So a 4 drive RAID 10 would have an MTBF of a single drive’s MTBF divided by 2. This still provides excellent MTBF compared to parity-based RAID [3].
Cost Comparison
When it comes to storage costs, RAID 10 arrays tend to be more expensive than RAID 5 or RAID 6 arrays on a per terabyte basis. This is because RAID 10 requires a minimum of 4 drives to implement while RAID 5 and RAID 6 can be created with just 3 and 4 drives, respectively.
For example, let’s say you want to create a 6TB array using 4TB drives. With RAID 10, you would need 4 drives for a total cost of 4 x $100 = $400 (assuming $100 per 4TB drive). This works out to $66 per TB of storage.
For RAID 5 with the same 6TB total capacity, you would only need 3 drives for a cost of 3 x $100 = $300. So the cost per TB is $50, or $16 cheaper than RAID 10.
With RAID 6, you need a minimum of 4 drives like RAID 10. So 4 x $100 = $400. But since you get 8TB of total capacity with 4 drives, the cost per TB is $50. Again, cheaper than RAID 10.
In general, the storage efficiency of RAID 10 is 50% while RAID 5 is 67% efficient and RAID 6 is 50-88% efficient depending on the number of drives. So RAID 10’s lower efficiency leads to higher $/TB costs.[1]
Ideal RAID 10 Use Cases
RAID 10 is ideal for use cases where performance is critical and the storage array size is smaller. Some examples include:
- Database servers – Databases require fast read/write speeds to quickly access and update records. RAID 10 provides low latency and high IOPS for transactional workloads like databases. According to Reddit users, RAID 10 is highly recommended for critical database deployments.
- Virtualization hosts – Hypervisors need to rapidly provision storage and quickly read/write virtual machine files. The parallelization of RAID 10 can significantly improve VM performance compared to other RAID levels.
- High performance compute clusters – HPC clusters demand fast scratch space for temporary files/results during complex computations. The striping in RAID 10 enables fast reads/writes for these temporary files.
- Real-time analytics – For real-time analytics on streaming data, RAID 10 delivers consistently fast performance crucial for processing data in real time with minimal latency.
In general, RAID 10 excels for mission critical applications where consistently low latency and high IOPS are essential. The tradeoff is RAID 10 is most practical for arrays up to around 8-12 drives. Beyond that, the cost and lower storage efficiency make other RAID levels or alternatives like ZFS more viable.
Alternatives to RAID 10
While RAID 10 offers a balance of performance and redundancy, there are some alternatives worth considering depending on your needs:
RAID 6 uses block-level striping with double distributed parity like RAID 5, but it provides fault tolerance up to two failed drives. This makes RAID 6 a good option when you need redundancy but don’t want the cost of multiple mirrored drives required for RAID 10. According to redditors on r/DataHoarder, RAID 6 is preferable for larger arrays if the slight performance hit is acceptable.
RAID 50 and RAID 60 are nested RAID levels that combine striping and mirroring for larger arrays. RAID 50 stripes data across multiple RAID 5 arrays, while RAID 60 stripes across RAID 6 arrays. These provide fault tolerance comparable to RAID 10 with less overhead for large arrays. However, rebuild times can be very long due to the multi-layered array.
For software-defined storage, some NAS operating systems like TrueNAS Core offer flexible RAID alternatives like ZFS striping with parity that provide redundancy without strict hardware RAID limitations.
RAID 10 Array Configurations
When setting up a RAID 10 array, one of the most important considerations is the number of drives to use. The minimum number of drives for RAID 10 is 4, but performance and capacity scale upward with more drives.
For optimal performance, aim for at least 6-8 drives in a RAID 10 array. This provides a good balance of redundancy and stripe size to maximize throughput. With fewer than 6 drives, the stripe size may be too small, limiting performance.
You also have a choice between dual drive mirrors (recommended) or single drive mirrors. Dual drive mirrors provide an extra layer of redundancy and allow the array to survive multiple drive failures. Single drive mirrors are less redundant but allow you to maximize capacity with fewer drives.
Overall, a 6-8 drive RAID 10 array with dual drive mirrors offers a great combination of performance, redundancy, and efficiency for NAS applications (Spiceworks).
Conclusion
In summary, some of the key pros of using RAID 10 for NAS include increased read/write performance, good redundancy, and the ability to withstand multiple drive failures. However, RAID 10 also comes with downsides like high cost and wasted storage capacity compared to other RAID levels.
Based on the analysis, RAID 10 is recommended for NAS in the following use cases:
- You need maximum performance for reads and writes
- Your NAS has more than 8 drives
- You prioritize redundancy over storage capacity
- Your NAS stores critical or frequently accessed data
For home or small business NAS with just 2-4 drives, RAID 10 may be overkill. RAID 5 or 6 can provide sufficient redundancy at a lower cost. Overall, RAID 10 is best suited for enterprise or mission-critical NAS where performance and redundancy are top concerns.
