RAID, which stands for Redundant Array of Independent Disks, is a data storage technology that combines multiple disk drive components into a logical unit. RAID provides increased storage performance, capacity, and reliability through redundancy. Two common RAID configurations are RAID 5 and RAID 10, which have different strengths and weaknesses. So which one is better – RAID 5 or RAID 10?
The quick answers to the key questions on RAID 5 vs RAID 10 are:
– RAID 5 is better for cost-efficiency and storage capacity, while RAID 10 is better for performance and reliability.
– RAID 5 requires a minimum of 3 drives, while RAID 10 requires a minimum of 4 drives.
– RAID 5 provides fault tolerance through parity, while RAID 10 provides fault tolerance through mirroring.
– RAID 5 has slower write speeds due to parity calculation, while RAID 10 has faster write speeds through striping.
– RAID 10 can survive multiple drive failures as long as the failed drives are in separate mirrors, while RAID 5 can only handle a single drive failure.
What is RAID?
RAID (Redundant Array of Independent Disks) is a data storage technology that combines multiple physical disk drives into a single logical unit to provide increased capacity, performance, and reliability for storing and accessing data. The main goals of RAID are:
- Increased data capacity – By combining multiple disk drives, total storage capacity is increased beyond the capacity of a single drive.
- Improved performance – Data can be distributed across multiple drives to enable parallel activity and faster reads/writes.
- Fault tolerance – Redundant data is provided through mirroring or parity so data can still be accessed in the event of drive failure.
There are several standardized RAID levels or architectures that provide different mechanisms to achieve these goals through drive configurations. Two of the most common ones are RAID 5 and RAID 10.
What is RAID 5?
RAID 5 is a widely used RAID level that provides a good balance of increased storage capacity and redundancy for data protection. Here are some key points about RAID 5:
- Requires a minimum of 3 disk drives
- Data is striped across all drives in the array
- Distributed parity is used to provide fault tolerance
- Parity allows recovery of data if one drive fails
- Typical RAID 5 arrays have 3-16 drives
- Total array capacity is equal to (N-1) x smallest drive capacity
- Write performance is slower due to parity calculation
In summary, RAID 5 provides fault tolerance through distributed parity, allowing for recovery from a single drive failure. The tradeoff is reduced write performance due to the parity computation.
RAID 5 Drive Failure and Rebuild
When a single drive in a RAID 5 array fails, the data contained on that drive can be rebuilt using the parity data spread across the remaining drives. For example, in a 3-drive RAID 5 array, if Drive 1 fails, the data that was on that drive can be recreated by taking the data from Drives 2 and 3 and calculating the parity.
During the rebuild process after a RAID 5 drive failure, the array is exposed to data loss in the event of an additional drive failure. The rebuild time is dependent on the drive capacity and can take many hours on large high-capacity drives.
What is RAID 10?
RAID 10 (also known as RAID 1+0), provides a combination of data mirroring and striping to deliver faster performance and high fault tolerance. Key points about RAID 10 configuration:
- Requires a minimum of 4 disk drives
- Data is mirrored across 2 drives
- Mirrored sets are then striped
- 50% redundancy due to mirroring
- Typical RAID 10 arrays have 4-16 drives
- Total capacity is 50% of total drive capacity
- Very high read/write performance due to striping
In summary, RAID 10 provides reliability through mirroring as well as fast performance through striping, but at the cost of 50% storage overhead due to the mirroring.
RAID 10 Drive Failure and Rebuild
With RAID 10, if a single drive fails, there is still an intact mirrored copy of that data available on the mirror drive. Rebuilding the RAID 10 array after a drive failure simply requires copying the data from the intact mirror drive to a new replacement drive. This provides faster rebuild times than parity-based RAID 5. RAID 10 can also survive multiple drive failures as long as the failed drives are in separate mirror pairs.
RAID 5 vs RAID 10: Comparison
Now that we’ve looked at the basics of RAID 5 and RAID 10, let’s compare them directly across some key factors:
| Factor | RAID 5 | RAID 10 |
|---|---|---|
| Minimum Drives | 3 | 4 |
| Fault Tolerance | Single drive failure | Up to failure of 1 drive per mirror |
| Redundancy Method | Distributed parity | Mirroring |
| Total Capacity | N-1 drive capacity | 50% of total capacity |
| Read Performance | Good | Excellent |
| Write Performance | Slow due to parity | Excellent due to striping |
| Rebuild Time | Slow due to parity recalculation | Faster as data is copied from mirror |
| Cost Efficiency | Excellent | Poor due to 50% redundancy overhead |
Based on this comparison, some key differences emerge:
- RAID 5 is more cost efficient and provides larger overall capacity for the same number of drives.
- RAID 10 provides faster performance, especially for write operations.
- RAID 10 offers higher fault tolerance, surviving multiple drive failures if drives in separate mirrors fail.
- RAID 5 has slower rebuild times and is exposed to greater data loss during rebuild.
When to Use RAID 5 vs RAID 10
Given the tradeoffs between performance, capacity, and redundancy, here are some general guidelines on when to use RAID 5 vs RAID 10:
Use RAID 5 When:
- Large storage capacity is needed
- Cost efficiency is important
- Performance demands are moderate
- Only single drive fault tolerance is required
RAID 5 provides excellent capacity and cost efficiency. It can meet performance needs for many workloads but may not suffice for mission critical high performance requirements.
Use RAID 10 When:
- Maximum performance is required
- High fault tolerance is needed
- Faster rebuild times are critical
- Cost is less of a concern
RAID 10 is best suited for applications where consistently high performance, maximum fault tolerance, and rapid recovery are top priorities, even at substantially higher cost.
RAID 5 vs RAID 10: Performance Impact
One of the biggest differences between RAID 5 and RAID 10 is in their performance characteristics, particularly for write operations. Due to the parity calculation, RAID 5 has slower write speeds. In contrast, RAID 10 offers faster reads and writes through its mirrored striping.
Here is a comparison of approximate sequential read and write speeds for RAID 5 and RAID 10 arrays of typical 7,200 RPM SATA drives:
| Operation | RAID 5 | RAID 10 |
|---|---|---|
| Sequential Read | 600 MB/s | 1200 MB/s |
| Sequential Write | 300 MB/s | 1000 MB/s |
As you can see, RAID 10 provides double the read performance and 3-4x faster writes compared to RAID 5. The performance limitations of RAID 5 write operations is due to the parity calculation overhead.
RAID 5 Write Penalty
The RAID 5 write penalty refers to the performance impact and slowdown caused by the parity computation on write operations. For each write to the RAID 5 array, the parity must be read, updated, and written across all the drives. This parity calculation causes up to a 4x slowdown for write speeds.
In contrast, RAID 10 does not suffer from this write penalty, as writes can be performed in parallel across the striped mirrored drives without any parity computation. This enables RAID 10 to deliver significantly faster write speeds.
RAID 5 vs RAID 10: Reliability
In addition to performance differences, RAID 5 and RAID 10 also differ in their fault tolerance capabilities and reliability:
- Fault Tolerance: RAID 5 can only tolerate a single drive failure, while RAID 10 can survive multiple drive failures as long as no two failed drives are within the same mirror.
- Redundancy: RAID 5 uses distributed parity to provide redundancy. RAID 10 uses mirroring, storing duplicate copies of data.
- Rebuild Times: Rebuilding a failed drive takes much longer with RAID 5 than RAID 10.
- Exposure: RAID 5 array is exposed to data loss during rebuilds, whereas RAID 10 maintains a mirrored copy during rebuilds.
In summary, RAID 10 provides stronger reliability through full duplication of data and faster rebuild capabilities. RAID 5 relies on more fragile parity and is exposed to greater risk of data loss during rebuilds.
Uptime and Availability
The higher fault tolerance and more rapid rebuild times of RAID 10 also provide benefits for system uptime and availability:
- Shorter RAID 10 rebuild times minimize time in degraded state after drive failures.
- Chance of unrecoverable data loss is lower with RAID 10 mirroring versus RAID 5 parity.
- RAID 10 can sustain multiple drive losses and stay operational if failures are in separate mirrors.
For mission critical systems that demand high uptime and availability, RAID 10 is generally a better choice over RAID 5 due to the more robust redundancy model and greater resilience to multiple drive failures.
RAID 5 vs RAID 10: Storage Efficiency
One area where RAID 5 clearly beats RAID 10 is in storage efficiency and overall capacity. Due to its mirroring redundancy, RAID 10’s usable capacity is always 50% of the total raw capacity. In contrast, RAID 5 arrays can efficiently utilize most of the raw capacity.
For instance, consider a RAID 5 and RAID 10 array both consisting of four 2 TB drives:
- RAID 5: Total raw capacity is 8 TB. With 1 drive used for parity, usable capacity is 6 TB.
- RAID 10: Total raw capacity is 8 TB. With 50% used for mirrors, usable capacity is 4 TB.
For the same number of disks, RAID 5 provides 50% more usable capacity. This difference is even more pronounced on larger arrays with more disks.
If storage efficiency and getting maximum capacity from available disks is critical, then RAID 5 is a better choice. However, for some workloads the superior performance and redundancy of RAID 10 outweighs the capacity limitations.
Cost Efficiency
The capacity difference between RAID 5 and RAID 10 also translates into a substantial impact on storage cost efficiency. RAID 10 essentially doubles the cost per gigabyte of storage versus RAID 5.
Using the example above, here is the cost efficiency comparison:
- RAID 5: 6 TB capacity from 4 drives. Cost per TB = 25% of drive cost
- RAID 10: 4 TB capacity from 4 drives. Cost per TB = 50% of drive cost
If budget constraints are a primary factor, the substantially better cost efficiency of RAID 5 makes it more appealing. RAID 10 delivers higher performance and redundancy at approximately double the cost.
Conclusion
In summary, there are good reasons to utilize both RAID 5 and RAID 10 depending on application requirements:
- RAID 5 offers excellent storage efficiency and cost savings for workloads that need large capacity but do not require top performance.
- RAID 10 provides unmatched speed, throughput, and redundancy for mission critical applications where performance and reliability are paramount.
RAID 5 is ideal for applications like backup and archival storage that call for high capacity at moderate speeds. RAID 10 excels at delivering maximum IOPS performance and minimal downtime for transactional databases, virtualization, and other demanding workloads.
By understanding the core differences between RAID 5 versus RAID 10, administrators can select the most appropriate RAID level to meet their specific technical and business requirements.
