RAID (Redundant Array of Independent Disks) is a technology that provides increased storage performance, redundancy, and reliability by combining multiple drives and distributing data across the array (https://www.techtarget.com/searchstorage/definition/RAID). SSD (Solid State Drive) is a storage technology that uses flash memory rather than spinning platters, providing much faster read/write speeds compared to traditional hard disk drives.
With the advent of SSDs, using them in a RAID configuration has become increasingly popular. SSD RAID combines the performance benefits of SSDs with the redundancy and reliability of RAID. Data can be distributed across multiple SSDs for faster throughput while also maintaining multiple copies for protection against drive failure (https://www.techtarget.com/searchstorage/definition/SSD-RAID-solid-state-drive-RAID).
Benefits of Using SSDs in RAID
SSDs provide significantly faster throughput and access times compared to traditional HDDs. By configuring multiple SSDs in a RAID array, you can further improve performance beyond what a single SSD can deliver.
Some of the key benefits of using SSDs in RAID include:
- Faster read and write speeds – Combining multiple SSDs increases the total available bandwidth for transferring data. For read-heavy workloads, RAID 0 can deliver close to the cumulative throughput of all drives.
- Lower latency – SSDs have very low seek times. RAID improves latency by distributing data across drives, allowing parallel access.
- Improved IOPS – SSDs provide high random I/O performance. Configuring SSDs in RAID enhances IOPS and reduces bottlenecks from a single drive.
- Redundancy – Certain RAID levels like 1, 5, 6, 10 provide fault tolerance by storing redundant data across drives. This protects against data loss if a drive fails.
SSD RAID arrays significantly outperform standalone HDDs and even HDD RAIDs. The ultra-fast speeds make SSD RAID ideal for applications like online transaction processing, virtualization, databases, and high-performance computing where fast data access is critical.
Challenges of Using SSDs in RAID
While SSDs provide many benefits for RAID implementations, they also come with some unique challenges. Two key challenges posed by SSDs in RAID are related to wear leveling and TRIM support.
Wear leveling is a process SSDs use to distribute writes evenly across all the blocks in the drive to optimize lifespan. However, wear leveling can cause data fragmentation issues in RAID arrays as blocks get shuffled around (Source). This can impact performance and make rebuilding a failed drive more complicated.
Another challenge is lack of proper TRIM command support in some RAID implementations. The TRIM command allows the SSD to reset blocks no longer in use and prepare them to be rewritten. If TRIM commands are not passed down correctly by the RAID controller, it can cause write amplification that reduces SSD performance and lifespan (Source). Proper TRIM support is essential for optimal SSD RAID performance.
RAID Levels Best Suited for SSDs
There are several RAID levels that can be effective when using SSDs, each with their own pros and cons:
RAID 0
RAID 0 (also called disk striping) spreads data across multiple drives with no parity or mirroring. This makes RAID 0 fast and efficient, but also risky since if one drive fails, all data will be lost (Jordan). The high speed of SSDs paired with RAID 0 provides excellent performance.
RAID 1
RAID 1 (disk mirroring) duplicates data across two or more drives, providing redundancy. Write speeds will be slower compared to RAID 0, but reads can be fast since data can be pulled from multiple disks. RAID 1 offers good overall performance and protection for SSDs.
RAID 5
RAID 5 stripes data across disks with distributed parity information. It requires at least three disks. RAID 5 provides good redundancy while maintaining faster speeds than RAID 1. The parity write penalty may impact performance with SSDs, but overall RAID 5 can be a good option.
RAID 10
RAID 10 is a nested/hybrid RAID combining mirroring and striping for speed and redundancy. However, it requires at least four disks. RAID 10 is popular for high performance SSD arrays, providing excellent speeds while also protecting data.
Maximizing SSD RAID Performance
To maximize the performance of SSD RAID configurations, there are several key factors to consider related to controllers, drivers, and settings:
First, use a high-quality RAID controller that is optimized for SSDs, like an LSI MegaRAID or Dell PERC controller. Avoid cheaper, consumer-grade RAID cards, as they can bottleneck SSD performance. Make sure to update the RAID controller firmware and drivers to the latest available versions for full SSD compatibility and performance improvements1.
Second, enable RAID write-back caching on the controller if supported. Write-back caching significantly reduces write latency by allowing the controller to immediately acknowledge writes before committing them to disk. However, ensure your controller has a backup power source like a battery or capacitor to prevent data loss on power failure.
Finally, tweak the array’s stripe size for optimal performance based on your workload. For mostly random I/O, use a smaller stripe size like 64KB. For sequential I/O, use a larger 128KB or 256KB stripe size. Benchmark different stripe sizes to determine the best option2.
Properly configuring the RAID controller and optimizing settings like stripe size allows SSD RAID to fully leverage the ultra-fast, parallel performance of multiple SSDs.
SSD RAID Setup Considerations
When setting up a RAID array with SSDs, there are a few key considerations to keep in mind for optimal performance:
SSD Selection
Not all SSDs are created equal, so it’s important to choose drives designed for enterprise or heavy workloads when building an SSD RAID array. Consumer-grade SSDs may be prone to failure under 24/7 operation and do not have the durability ratings for RAID environments. Look for SSDs with high endurance ratings, strong enterprise features like power loss protection, and a 5 year warranty or longer. Some good SSD options include the Samsung PM1633a, Micron 5100 ECO, and Intel DC D7 series.
Configuration
SSDs configured for RAID will require setting the RAID mode in the SSD firmware, along with configuring RAID in the operating system or hardware RAID controller. Ensure TRIM is enabled to maintain performance. Some SSDs also have overprovisioning modes that reserve extra space for wear leveling and garbage collection – enabling this can help with endurance and performance consistency over time. Finally, align partitions properly and do not use disk compression.
SSD RAID Maintenance Best Practices
Proper maintenance is crucial for SSD RAID arrays to ensure optimal performance and longevity. Here are some best practices:
Monitor SSD health – Use SMART monitoring tools to keep an eye on metrics like wear leveling count, total data written, and bad blocks. This allows you to identify potential failures before they happen.
Refresh drives periodically – SSDs have a finite write endurance. Periodically replacing drives proactively can prevent unexpected failures. For RAID 1, 5, and 10, drives can be replaced one at a time with no downtime.
Keep firmware updated – Firmware updates often include bug fixes, performance improvements, and enhanced SSD lifecycle management. Keep drives updated to the latest stable firmware versions.
Use TRIM and garbage collection – Enable TRIM support if using hardware RAID. For some software RAID, garbage collection helps maintains performance by actively erasing deleted data blocks.
Monitor array health – Keep an eye on the overall RAID array health, not just individual drives. Degraded arrays or disks need to be addressed promptly.
Test recoverability – Periodically test the recoverability of a degraded array by intentionally failing a disk. This confirms the array can rebuild smoothly when necessary.
Control drive vibration – Excess vibration can reduce SSD lifespan. Use drive bay mounts, chassis dampening, and solid state disks to control vibration.
Keep spare drives – Have compatible spare SSDs ready to rebuild a failed drive quickly. Minimal downtime is essential for high uptime requirements.
Follow manufacturer guidelines – Check drive manufacturer recommendations on usage conditions, maintenance, and environmental factors like temperature.
Case Studies/Examples
SSD RAID setups have been implemented successfully in real-world scenarios, demonstrating their performance and reliability benefits. One case study from Kingston Technology examined replacing hard drives with SSDs in a RAID 5 array for a media production company (Source 1). After the upgrade to SSDs, they saw dramatic improvements in render times for video production, with up to 9x faster performance. This allowed the company to take on more client work and reduce costs.
Another case study from Graid Technology looked at combining SupremeRAID with Solidigm D5-P5316 QLC NVMe SSDs (Source 2). Their testing showed SSD RAID delivered over 13 million IOPS and high bandwidth while maintaining data protection. For enterprise applications needing high throughput, SSD RAID delivered substantial gains over traditional HDD RAID.
These real-world examples demonstrate the performance, reliability, and cost benefits possible for video production, enterprise applications, and other high data throughput use cases using SSD-based RAID.
Limitations of SSD RAID
While SSD RAID offers some benefits, there are some limitations to consider as well:
Cost – SSDs are more expensive per gigabyte compared to traditional HDDs. As a result, building SSD RAID arrays can be very costly, especially for large storage capacities. According to one analysis, SSD RAID arrays can cost 5-10x more than comparable HDD RAID solutions (source).
Complexity – Configuring and managing SSD RAID arrays requires more technical expertise compared to HDD RAID. Factors like TRIM support, write amplification, and wear leveling require careful configuration for optimal SSD RAID performance (source). Regular monitoring and maintenance are also recommended.
While the benefits are substantial, the added costs and complexity should be evaluated before implementing SSD RAID, especially for large deployments.
Conclusion
In summary, SSDs can provide significant performance benefits when used in RAID configurations due to their fast read/write speeds and low latency. However, SSDs also come with unique considerations around wear leveling, TRIM support, and disk replacement that need to be accounted for.
RAID 0 and RAID 10 configurations are generally recommended for SSD RAID to maximize speed benefits. RAID 5 and 6 can also work well, provided the controller supports TRIM and disk scrubbing. Limiting the RAID write cache size can help reduce write amplification on the SSDs.
When setting up and maintaining an SSD RAID, enable TRIM, monitor disk health closely, and have hot spares ready for replacement. Frequent backups are also critical to protect against potential multiple disk failures. While SSD RAID can deliver exceptional performance, it does come with more hardware considerations than traditional hard drive RAID.
In conclusion, with careful configuration and maintenance, SSD RAID allows combining the performance of SSDs with the redundancy and speed benefits of RAID. For applications requiring fast storage throughput and low latency like databases, virtualization, media editing and more, SSD RAID is an excellent high-speed storage solution.