RAID 10, also known as RAID 1+0, is a hybrid RAID configuration that combines disk mirroring and disk striping to provide fault tolerance and improved performance. RAID 10 is best suited for applications that require high levels of performance and redundancy.
What does RAID 10 do?
RAID 10 provides a balance of speed and data protection by mirroring data across pairs of drives and then striping the mirrored data across multiple drive pairs. This results in fast read/write speeds from the striping along with redundancy from the mirroring.
In a basic 4-drive RAID 10 configuration, data is written in identical copies to two drives simultaneously (mirroring). Those mirrored pairs are then striped across the drive array, with a portion of the data on each pair. If one drive fails, its mirror still has a complete copy of the data. This provides fault tolerance.
What are the advantages of RAID 10?
Some key advantages of RAID 10 include:
- High throughput – Reads and writes are fast since data is striped across multiple drives.
- Redundancy – Complete copies of all data are maintained through mirroring, providing fault tolerance.
- Ability to survive multiple drive failures – RAID 10 can withstand up to half of the drives failing (all from different mirrors).
- Ideal for transactional workloads – The combination of speed and redundancy make it well-suited for databases.
- Easy to recover – Data can be rebuilt after a failure using the existing mirror copy.
What are the disadvantages of RAID 10?
Some potential downsides of RAID 10 include:
- Higher cost – Requires at least 4 drives to implement, increasing storage costs.
- Lower capacity – Since data is mirrored, total usable capacity is 50% of total drives.
- Rebuilding can be slow – Recreating a failed drive’s data from its mirror can take time.
- Performance impact if too many drives fail – More than 1 failure per mirror degrades performance.
When should you use RAID 10?
Here are some ideal usage scenarios for implementing RAID 10:
- Transactional databases – Provides fast data access along with fault tolerance.
- Mission critical applications – Critical apps demand both high performance and redundancy.
- Virtualization and large server workloads – Serves resource intensive applications efficiently.
- High performance computing – Delivers speed for modeling, simulations and analytics.
- Video editing and media streaming – Fast access to huge files sizes improves workflows.
In general, RAID 10 excels at delivering both speed and redundancy for systems running I/O intensive applications that need maximum uptime.
When should you avoid RAID 10?
RAID 10 may not be the best choice when:
- Cost savings are a priority – RAID 10 is expensive, requiring at least 4 drives.
- Capacity is paramount – The mirroring in RAID 10 cuts usable space in half.
- Redundancy needs are lower – For less critical data, RAID 5 or 6 offer redundancy more affordably.
- Performance needs are lower – For basic storage needs, a RAID 0 array may provide enough speed.
In general, you should avoid RAID 10 in situations where redundancy and extreme performance are less important than drive utilization and storage costs.
How does RAID 10 compare to other RAID levels?
RAID 10 differs from other common RAID configurations in the following ways:
| RAID Type | Data Redundancy | Performance | Minimum Drives |
|---|---|---|---|
| RAID 0 | None | Excellent | 2 |
| RAID 1 | Excellent | Good | 2 |
| RAID 5 | Good | Good | 3 |
| RAID 6 | Excellent | Fair | 4 |
| RAID 10 | Excellent | Excellent | 4 |
RAID 10 provides a blend of redundancy and performance that you cannot get from other single RAID levels. By combining mirroring and striping, it delivers both speed and protection better than RAID 1 or RAID 5 alone.
How is RAID 10 implemented?
There are two main ways to architect and configure a RAID 10 array:
RAID 1+0
Disks are first mirrored and then striped. Provides optimal performance but less flexible disk counts (even number of drives needed).
RAID 0+1
Disks are first striped and then mirrored. More flexible drive counts but performance less optimized. Still fast due to striping.
Both provide the core RAID 10 benefits of redundancy and speed. RAID 1+0 is considered the preferred method on hardware RAID controllers since it better optimizes the stripe layout.
What are the ideal number of drives for RAID 10?
Common drive counts for RAID 10 arrays include:
- 4 drives – Minimum required to implement RAID 10. 2 mirrors with 2-drive stripes.
- 6 drives – 3 mirrors, 2 drives each, striped as 3-drive stripes.
- 8 drives – 4 mirrors striped as 4-drive stripes. Common and provides optimal performance.
- 10 drives – 5 mirrors striped across 5 drives each. Can suffer performance issues.
The most common drive counts are 4, 8, or 16. 8 drives provide strong performance for most implementations. Avoid prime number drive counts (like 5 or 7).
What RAID controllers and hardware support RAID 10?
Most hardware and software RAID solutions today support RAID 10, including:
- Hardware RAID cards – From vendors like LSI, Dell, HP, Adaptec, and more.
- Motherboard RAID – Some motherboards have built-in RAID controllers.
- Operating system RAID – Software RAID through Windows, Linux, etc.
- Dedicated RAID enclosures – External enclosures with built-in RAID.
- Virtual RAID – RAID through virtualization platforms like VMware or Hyper-V.
Choosing the right RAID controller depends on factors like performance, availability, and budget. Hardware RAID cards generally provide the best performance.
How do you configure RAID 10?
Configuring RAID 10 involves these key steps:
- Check RAID controller documentation and utilities
- Install matching drives in the RAID enclosure
- Open the RAID configuration utility
- Select create new array and choose RAID 10
- Select the physical disks to include
- Specify additional options like stripe size
- Initialize the array to start building it
- Monitor RAID status until synchronization finishes
Many RAID controllers include setup wizards to guide you through the process. Always use matching disks in terms of type, size, and speed.
How do you monitor and manage a RAID 10 array?
Monitoring and managing RAID 10 requires periodically checking the status of the array through tools like:
- RAID controller management utility
- Server management software
- Operating system admin tools
- Third-party RAID monitoring tools
Look for any indications of disk failures, synchronization issues, or degraded performance. Take actions like replacing failed drives promptly to avoid having multiple failures.
How do you recover a failed drive in RAID 10?
Recovering from a failed drive in RAID 10 involves:
- Identifying the failed drive through management tools.
- Replacing the failed physical drive with a compatible spare.
- Allowing RAID controller to automatically rebuild failed mirror to the new drive.
- Monitoring rebuild progress until complete.
- Verifying synchronized status and operation when finished.
The rebuilding process copies data from the surviving mirror drive to the replacement to restore redundancy. The time to rebuild depends on the drive size and controller speed.
Can you expand the size of a RAID 10 array?
Expanding a RAID 10 array is possible by:
- Adding an entire new mirror set of drives to expand capacity.
- Replacing all existing drives with larger ones to gain more space.
- Migrating to larger striped block sizes to utilize more of the underlying drive capacities.
Expanding by adding full mirrors allows growth while minimizing rebuild times. Replacing all drives has longer rebuild risks. Increasing striped block size avoids rebuilds but requires backups and migration.
Can you convert another RAID to RAID 10?
Converting an existing RAID configuration like RAID 5 or RAID 6 to RAID 10 is possible through migration but has challenges:
- Requires adding at least as many new drives as current array has.
- Needs temporary storage to back up existing data while reconfiguring.
- Data must be fully copied over to new RAID 10 drives and volumes.
- Can result in data loss if failures occur during migration.
Because of the risks, migrating existing RAIDs to RAID 10 should only be done when absolutely required. It is often safer to copy data to a new RAID 10 array instead.
Conclusion
RAID 10 delivers an exceptional balance of performance and fault tolerance by combining disk mirroring and striping. It provides speed through striping along with redundancy from mirroring. RAID 10 works well for mission critical databases, virtualization, media streaming, and other high performance applications that demand 24/7 uptime. While RAID 10 has higher cost and lower capacity, its blend of speed and reliability make it a valuable RAID choice for the right workloads.