RAID 10, also known as RAID 1+0, is a hybrid RAID configuration that combines disk mirroring and disk striping to provide both performance and redundancy for hard disk drives. In this article, we’ll take an in-depth look at what RAID 10 is, how it works, and what it looks like in practice.
What is RAID 10?
RAID 10 requires a minimum of 4 drives and combines mirroring and striping by creating a stripe of mirrors. This means the data is mirrored (copied) onto another drive, and then the mirrors are striped across the drives. The resulting array has the performance advantages of RAID 0’s striping and the fault tolerance of RAID 1’s mirroring.
Advantages of RAID 10
- Very high I/O performance – Reads and writes are spread across multiple drives for faster speed
- Very robust fault tolerance – Data remains safe even if multiple drives fail
- Ideal for high demand transactional applications like databases
- Rebuild times are faster than with RAID 5 or 6
Disadvantages of RAID 10
- More expensive since it requires at least 4 drives
- Half of total capacity is used for redundancy
How Does RAID 10 Work?
RAID 10 works by creating a mirror of two drives and then striping data across the mirrors. Here is an illustration of how it works in a 4-drive setup:
- Two drives are mirrored to create a RAID 1 array.
- The other two drives are also mirrored to create another RAID 1 array.
- Data is striped across the two RAID 1 arrays.
This results in a total of 4 disks that appear as a single volume to the operating system. RAID 10 provides performance improvements from the striping as well as redundancy from the mirroring. If any single drive fails, the mirror on the other drive can still provide access to data without downtime.
RAID 10 Configurations
There are several possible configurations for RAID 10 depending on the number of drives used. Here are some of the most common setups:
4 Drive RAID 10
The minimum number of drives required for RAID 10 is 4. With 4 drives, two RAID 1 mirrors are created and then data is striped across them:
| Disk 1 | Disk 2 |
| Mirrored | Mirrored |
| Disk 3 | Disk 4 |
| Mirrored | Mirrored |
6 Drive RAID 10
With 6 drives, 3 RAID 1 mirrors can be created and striped. This provides an extra mirror for additional redundancy:
| Disk 1 | Disk 2 |
| Mirrored | Mirrored |
| Disk 3 | Disk 4 |
| Mirrored | Mirrored |
| Disk 5 | Disk 6 |
| Mirrored | Mirrored |
8 Drive RAID 10
With 8 drives, 4 RAID 1 mirrors can be created and striped. This provides maximum performance and redundancy in an 8-drive setup:
| Disk 1 | Disk 2 |
| Mirrored | Mirrored |
| Disk 3 | Disk 4 |
| Mirrored | Mirrored |
| Disk 5 | Disk 6 |
| Mirrored | Mirrored |
| Disk 7 | Disk 8 |
| Mirrored | Mirrored |
RAID 10 Rebuild Process
One of the advantages of RAID 10 is that rebuild times are faster compared to other redundant RAID levels. Here is what the rebuild process looks like if a disk fails:
- If a disk fails, the RAID controller disables access to the failed drive and the mirror drive takes over responsibility for all data.
- A replacement drive is inserted to replace the failed drive.
- The data from the mirror drive is simply copied to the replacement drive.
- When copying is complete, the rebuild is finished and full redundancy is restored.
This rebuild process is faster because unlike parity-based RAID, RAID 10 does not have to recalculate parity. It simply duplicates the data from the remaining mirror drive. The larger the RAID 10 array, the more options there are for which mirror drive’s data can be copied to the replacement drive.
When to Use RAID 10
Here are some key advantages of RAID 10 that make it a good choice for certain use cases:
Transactional Databases
Databases require very fast read and write performance. RAID 10 delivers fast I/O operations ideal for heavy database workloads. The redundancy also helps protect against downtime if a drive fails.
Mission Critical Applications
For business critical applications where maximum uptime is crucial, RAID 10 provides excellent redundancy to keep things running even during a drive failure.
High Traffic Websites
Popular websites need to sustain heavy traffic with consistently low latency. The performance of RAID 10 is ideal for supporting many concurrent readers and writes.
Video Editing
Video production involves reading and writing large files very quickly. RAID 10 excels at this with fast throughput for enhanced productivity.
When Not to Use RAID 10
Here are some cases where other RAID levels may be more suitable than RAID 10:
Archival Storage
If data will rarely be accessed, capacity is more important than performance. RAID 5 or 6 would provide sufficient redundancy with greater storage capacity.
Non-Critical Applications
For systems where absolute uptime is not crucial, the extra cost of RAID 10 may not be justified. A single disk or RAID 0 could suffice.
Read-Intensive Workloads
For workloads involving mainly data reads, RAID 5 can provide adequate performance with better overall capacity.
Cost-Sensitive Environments
If budget is a major concern, the cost of multiple disks for RAID 10 may be prohibitive. RAID 6 offers redundancy with fewer disks.
Conclusion
RAID 10 combines both high performance and fault tolerance by striping and mirroring drives. It requires a minimum of 4 drives and provides fast rebuilding when a disk fails. RAID 10 is ideal for transactional databases, critical business applications, high traffic websites, and video editing where both speed and redundancy are crucial.
The tradeoffs are higher cost and lower overall storage capacity compared to other RAID levels. Organizations should weigh their specific performance, uptime, and budgetary needs to determine if RAID 10 is the right choice.