When setting up a NAS (network-attached storage) system, one of the most important choices is which RAID level to use. The RAID level determines how data is distributed across the hard drives to balance performance, capacity, and fault tolerance. There are several common RAID levels used for NAS systems, each with their own pros and cons. In this comprehensive guide, we will examine the most popular RAID levels for NAS and provide recommendations based on different usage scenarios.
What is RAID?
RAID stands for Redundant Array of Independent Disks. It is a method of using multiple hard drives together to enhance performance and/or provide data protection. The key benefits of RAID include:
- Increased read/write performance – spreading data across multiple drives allows for parallel activity.
- Greater capacity – multiple drive capacities are combined into a single volume.
- Redundancy – duplicate copies of data provide fault tolerance.
There are several standard RAID levels, each with specific design tradeoffs. The most common ones used in NAS systems are:
RAID 0
RAID 0, also known as striping, spreads data evenly across all drives with no redundancy. RAID 0 provides better performance but no protection against drive failure.
RAID 1
RAID 1, also known as mirroring, duplicates all data on a second drive to provide redundancy. Half the available capacity is used for backup.
RAID 5
RAID 5 stripes data across all drives with parity blocks distributed evenly amongst them. This allows for single drive failure recovery with minimal capacity loss.
RAID 6
RAID 6 is similar to RAID 5 but with double distributed parity providing protection against failure of up to two drives.
RAID 10
RAID 10 combines mirroring and striping by creating mirrored pairs of drives and striping data between each set. Provides high performance along with fault tolerance.
Factors to Consider for NAS RAID Level
Choosing the appropriate RAID level involves balancing performance, capacity, and fault tolerance. Here are some key factors to consider:
- Read/write performance – Some levels provide faster data transfers than others. RAID 0 and 10 are generally the fastest for typical workloads.
- Capacity efficiency – RAID 5, 6 and 10 incur some storage overhead for parity/mirroring. RAID 0 provides 100% capacity.
- Rebuild times – The time to rebuild an array after a disk failure is an important factor for fault tolerance.
- Number of drives – Some RAID levels have minimum drive requirements. RAID 6 requires at least 4 drives.
Usage patterns are also important. For example, whether the NAS will be used for random access or large sequential transfers affects the performance differences of each level. The criticality of the data is a key factor determining how much redundancy is needed.
Recommended RAID Levels for Home/SOHO NAS
For home and small office NAS systems, performance and capacity are often the priorities while fault tolerance may be less critical. Here are typical recommendations for home/SOHO use cases:
2 to 4 Drive NAS
- RAID 0 – Optimized for capacity and performance. Lacks redundancy but costs are low.
- RAID 1 – Simple mirroring provides fault tolerance though at 50% capacity overhead.
4+ Drive NAS
- RAID 5 – Good option combining reasonable performance, capacity and redundancy for personal storage.
- RAID 10 – Mirroring plus striping offers faster speeds. Somewhat lower capacity due to mirroring overhead.
RAID 6 is overkill for home use unless storing highly critical data. The performance costs versus RAID 5 make it less ideal for typical home workloads. RAID 0 provides maximum performance and capacity but lacks any redundancy.
Recommended RAID Levels for Business/Enterprise NAS
Business and enterprise NAS systems store important data and therefore fault tolerance becomes a higher priority. Performance is still important for supporting multiple concurrent users. Capacity efficiency is also desired to minimize storage costs. Here are typical recommendations for business NAS deployments:
General Business Storage
- RAID 5 – Provides a good blend of performance, capacity and single drive fault tolerance.
- RAID 6 – The extra parity drive makes RAID 6 suitable for business critical data where uptime is important.
High Performance Business Storage
- RAID 10 – Combining striping and mirroring yields faster speeds for supporting demanding workloads.
Business Archives/Backups
- RAID 6 – Maximum redundancy is ideal for archival data where rebuild times are less critical.
For transactional databases or other IO-intensive applications, a higher performance dedicated RAID controller may be preferred over software RAID. This allows for caching, battery-backup, and other optimizations.
Recommended RAID Levels for Media Production/Post-Production NAS
For media production environments processing and storing large video files, high performance and capacity are the top considerations:
- RAID 5 – Cost-effective option providing striping performance with acceptable redundancy.
- RAID 6 – Provides an extra parity drive over RAID 5 for critical media assets.
- RAID 10 – Optimized for performance editing/streaming demanding video formats.
Due to the large storage requirements for uncompressed media, capacity efficiency is important as well. RAID levels sacrificing too much total capacity for redundancy may require supplementing with separate archives.
How Many Drives Are Needed for RAID?
The number of hard drives required depends on which RAID level you choose:
| RAID Level | Minimum Drives |
| RAID 0 | 2 |
| RAID 1 | 2 |
| RAID 5 | 3 |
| RAID 6 | 4 |
| RAID 10 | 4 |
More drives can be added to array as needed for additional capacity and/or performance. However, a minimum number of drives are required depending on the RAID level.
Choosing the Right File System for NAS RAID
In addition to selecting a RAID level, the choice of file system is also important for NAS configurations. Here are some popular file system options to consider:
EXT4
The EXT4 file system is commonly used with Linux-based NAS platforms. It provides good performance and reliability for general storage workloads.
Btrfs
Btrfs is a newer copy-on-write file system for Linux providing efficient snapshotting and incremental backups.
ZFS
ZFS was originally developed for Solaris and optimized for storage pools. It offers advanced data integrity checking and self-healing capabilities.
XFS
XFS excels at handling large files with high throughput making it suitable for multimedia storage and large file transfers.
NTFS
NTFS is the standard Windows file system providing full support for Windows permissions, encryption, compression, etc.
For cross-platform NAS systems, NTFS provides the best compatibility for sharing files between Windows, macOS, and Linux. But native Linux file systems like EXT4 and Btrfs have advantages for Linux-based NAS distros.
RAID Controller: Hardware vs Software
A RAID controller manages the distribution of data across the array. There are two main implementation options:
Hardware RAID Controller
- Dedicated controller card or processor providing RAID management.
- Offloads RAID computations from main CPU for better performance.
- More expensive but higher performance than software RAID.
Software RAID
- RAID is implemented by OS kernel and device drivers.
- No specialized hardware needed making it more affordable.
- CPU has added workload of RAID processing.
Software RAID provides a cost-effective option for many consumer NAS deployments. But for mission critical storage, the performance and reliability of hardware RAID is preferable.
How To Choose the Right NAS RAID Level
Choosing the optimal RAID level for your NAS involves weighing a number of factors:
- Storage capacity needs – Higher capacity efficiency allows fitting more storage within your budget.
- Performance requirements – Match RAID performance characteristics to your workloads.
- Availability needs – Consider fault tolerance and rebuild times based on uptime requirements.
- Number of drives – Available drive bays may dictate which RAID levels are practical.
- Budget constraints – Certain levels require more drives which increase costs.
For home and SOHO users, RAID 5 provides a good blend of performance, capacity and redundancy for general use. RAID 1 gives up capacity for easy mirroring. RAID 0 maximizes storage and speed but has no fault tolerance.
For higher capacity business storage, RAID 6 offers an extra parity drive over RAID 5 for critical data protection. RAID 10 balances performance and redundancy for demanding workloads but at increased cost.
Always consider future storage needs and budget for expansion when choosing your initial NAS RAID level. Leveraging higher capacity drives can provide more room to grow within a given RAID level.
Transitioning Between RAID Levels
The ability to transition between different RAID levels allows adjusting to changing performance and capacity requirements. However, options for transitions are limited based on the following factors:
- RAID types (standard vs nested) – Some levels like 1+0 are more complex nested RAID.
- Existing drive configurations – Available capacity and compatibility impact transitions.
- Need for adding/removing drives – Changing drive quantities may enable different RAID levels.
- Data preservation requirements – Migrating levels may require recreating the array and moving data.
The simplest transitions are growing drive quantities within a given level. For example, expanding a RAID 5 array with larger drives or additional drive bays. Transitions requiring restriping data to a new RAID format involve more risk and downtime.
Tools are available to assist with RAID migrations while minimizing disruptions. But comprehensive backups are still essential prior to altering underlying storage architectures.
Best Practices for Configuring NAS RAID
Proper configuration is crucial to building a reliable and high performance NAS RAID. Here are some key best practices to follow:
- Choose enterprise class drives designed for NAS workloads (high endurance, vibration resistance, etc). Consumer drives may have inadequate reliability.
- Use drives of the same model and capacity – mixing models/capacities can impair performance.
- Configure a hot spare if drive swapping is difficult – Allows automatic rebuild if a drive fails.
- Align partitions properly – Ensures data is striped optimally across drive boundaries.
- Tune the array block size – Larger blocks benefit sequential access while smaller ones favor random IOPS.
Test configurations thoroughly under realistic workloads. Monitor for performance bottlenecks, adequate throughput, and proper fault tolerance before deploying to production.
Maintaining Your NAS RAID
Regular maintenance helps sustain performance and reliability of your NAS RAID:
- Monitor drive health statistics for signs of potential failure.
- Perform periodic surface scans to identify latent bad sectors.
- Check and upgrade firmware when new versions are available.
- Clean air filters and test cooling fans in dust-prone environments.
- Replace aging drives proactively to avoid degraded arrays.
Tuning and reallocating storage across volumes may be warranted as usage patterns evolve. Backup NAS data periodically to allow rebuilding arrays in the event of multiple drive failures exceeding fault tolerance limits.
Conclusion
Choosing the right RAID level involves balancing performance, capacity, and fault tolerance for your specific needs. For home NAS systems, RAID 5 provides a good combination of these factors while RAID 0 or 1 may be preferred if optimizing for storage capacity or redundancy respectively.
For enterprise solutions, RAID 6 offers an extra drive failure tolerance over RAID 5 with minimal capacity loss. RAID 10 combines mirroring and striping for the highest throughput but at increased cost. Media production environments can also leverage RAID 5, 6, or 10 depending on their performance and storage demands.
Always factor in room for storage growth needs. Transitions between RAID levels are possible but may require data migration. Proper configuration and maintenance is key to building reliable, high performance NAS storage.
The wide selection of RAID options provides the flexibility to tailor your NAS to meet your specific technical requirements, budget, and data availability needs.