Network Attached Storage (NAS) devices are a convenient way to provide shared storage and backup solutions for home and business users. One key consideration when setting up a NAS is whether to configure the drives in a RAID array. RAID offers redundancy and potential performance benefits, but also carries some downsides. This article examines the pros and cons of using RAID with NAS to help you decide if it’s the right choice for your needs.
What is RAID?
RAID stands for Redundant Array of Independent Disks. It is a method of combining multiple physical drives into a single logical drive to provide increased capacity, performance, and/or reliability compared to a single drive.
There are several different RAID levels, each with its own mix of benefits and drawbacks:
- RAID 0 – Data is striped across multiple drives for faster performance, but there is no redundancy. If one drive fails, all data will be lost.
- RAID 1 – Drives are mirrored for full redundancy, but storage capacity is halved. High read speeds, but slow writes.
- RAID 5 – Data and parity information is striped across 3+ drives. Can survive one drive failure without data loss.
- RAID 6 – Same as RAID 5, but can survive two drive failures.
- RAID 10 – Combination of RAID 0 striping and RAID 1 mirroring. Fast performance with redundancy.
The specific RAID level you choose depends on your priorities for performance, capacity, and fault tolerance. Many NAS devices support multiple RAID configurations.
Benefits of using RAID with NAS
Here are some of the potential advantages of configuring your NAS drives in a RAID array:
Redundancy and fault tolerance
The key benefit of RAID is protection against drive failures. With the right RAID level, your data will remain intact even if one (or more) drives completely fail. This is essential for safeguarding important data and maintaining uptime.
Increased performance
By striping data across multiple drives, RAID can provide performance improvements compared to a single drive. Access times are faster since data is distributed across disks. RAID 0 offers the biggest speed boost but no redundancy, while RAID 10 balances both speed and redundancy.
Capacity expansion
RAID allows you to combine multiple physical drives into a single logical volume. This can give you more usable storage capacity compared to standalone drives, apart from RAID 1 which mirrors drives.
Read performance and caching
RAID levels that stripe data evenly across disks can deliver faster sustained read speeds by distributing disk I/O. The controller can also take advantage of cached data rebuilding from the array after a drive failure.
Downsides of using RAID with NAS
While RAID has some clear benefits, there are also some potential drawbacks to consider:
Increased complexity
Configuring and managing a RAID array adds complexity compared to standalone drives. Choosing the right RAID level and properly maintaining the array requires knowledge and experience. RAID management tools can ease this burden.
Lower usable capacity
Depending on the RAID level, the total usable capacity may be lower than the sum of the individual drives. RAID 1 halves available storage by mirroring drives. Parity and striping overhead in other RAID levels also slightly reduces usable space.
Slower rebuild times
Rebuilding a failed drive in a RAID array can be a lengthy process, taking hours or days with large high-capacity drives. During this time, the array is vulnerable to a second drive failure.
No redundancy for logical failures
While RAID protects against physical drive failures, it does not safeguard against “logical failures” like file corruption or accidental deletion. You still need backup solutions like snapshots and offsite backups to guard against data loss.
Higher cost
Implementing RAID requires additional drives, which increases upfront storage costs. There may also be added costs for advanced RAID controller cards and enterprise-class drives designed for RAID environments.
Should you use RAID 0, 1, 5, 6, or 10?
If you decide to use RAID with your NAS, the next question is which RAID level to choose. Here’s an overview of key factors to consider for each option:
RAID 0
- Fast performance, but no redundancy
- Good for scratch disks where redundancy isn’t required
- Avoid for critical data or sole backup target
RAID 1
- Total redundancy by mirroring drives
- 2x storage cost for same usable capacity
- Ideal for smaller NAS configurations
RAID 5
- Good balance of redundancy and storage efficiency
- Minimum of 3 drives required
- Caution with larger drive capacities due to long rebuild times
RAID 6
- Can survive two drive failures by using dual parity
- Minimum 4 drives, higher storage overhead
- Preferred for large arrays with high drive failure risk
RAID 10
- Provides speed and redundancy by striping mirrors
- 50% storage efficiency
- Expensive, but ideal for performance-critical applications
The “best” RAID level depends on your specific goals – capacity, speed, redundancy, and budget are key considerations.
Is RAID necessary for NAS?
For home and small business NAS devices, RAID may provide minimal advantages. Here are some cases where you may not need RAID:
- If the NAS is only for backup or non-essential data
- Lower drive count (2-4 drives) where rebuild times are manageable
- Adequate redundancy from cloud backups or other NAS units
- Budget constraints make RAID cost-prohibitive
For critical business data or performance-intensive workloads, RAID offers clearer benefits. But for many consumer or basic business needs, RAID may be unnecessary.
Is software or hardware RAID better?
RAID can be implemented in two ways:
- Hardware RAID – Uses a dedicated RAID controller card and processor
- Software RAID – Managed by the operating system using the system CPU
Hardware RAID advantages:
- Frees up system CPU resources
- Provides caching and I/O optimization
- More reliable with dedicated hardware controller
Software RAID advantages:
- Much lower cost by avoiding RAID card purchase
- Easier to manage drives independently from system
- Potentially supports more RAID levels and configurations
For simple home or small business NAS setups, software RAID is generally sufficient. Hardware RAID becomes important for mission critical systems that demand highest performance and reliability. The NAS device itself will often dictate which RAID implementation it uses.
How many drives do you need for RAID?
The minimum number of drives needed for RAID depends on the RAID level:
- RAID 0 – Minimum 2 drives
- RAID 1 – Minimum 2 drives
- RAID 5 – Minimum 3 drives
- RAID 6 – Minimum 4 drives
- RAID 10 – Minimum 4 drives
In general, more drives is better for both increased capacity and spreading parity information across disks. But you need to balance drive cost against realistic storage needs. For home NAS, 2-4 drives often provides a good capacity-to-cost ratio when paired with cloud backups.
Should you use same size drives in RAID?
For RAID arrays, it’s strongly recommended to use same-capacity drives from the same manufacturer and model line. Mixing drives introduces several potential issues:
- Total capacity limited to smallest drive size
- Uneven stripe sizes can impair performance
- Increased risk of rebuild failures after drive swap
Using identical drives avoids mismatch complications and allows you to easily swap in spares. Enterprise RAID systems can work with mixed drive sizes, but for consumer NAS you’re best sticking with matched drives.
Is RAID 1, 5, or 10 more reliable?
All three of these popular RAID levels provide fault tolerance through redundancy, but they protect your data in different ways:
- RAID 1 – Mirroring means all data is copied twice for full redundancy. Rebuild times are faster since only one drive needs copying.
- RAID 5 – Parity allows one drive failure tolerance. But long rebuild times leave a second failure risk.
- RAID 10 – Striped mirrors provide redundancy with high performance. But more storage overhead than RAID 5.
For reliable protection, RAID 10 is the safest choice while RAID 5 offers good redundancy at lower cost. RAID 1 is also robust for two-drive NAS setups. Regular backups are still recommended no matter which RAID level you choose.
Can you combine RAID levels?
Combining multiple RAID levels across different drive groups, also known as nested RAID, is possible with some RAID controllers. For example:
- RAID 1+0 – Stripes data across mirrored drive pairs
- RAID 5+0 – Mirrors striped RAID 5 arrays
- RAID 0+1 – Mirrors striped drive groups
These nested RAID configurations provide a balance of features from the combined levels. However, they require a large number of drives and add significant complexity. For most home and small business NAS use cases, a single RAID level is appropriate and easiest to manage.
What RAID level is most cost effective?
The most cost-effective RAID option depends on your capacity needs versus redundancy requirements:
- RAID 0 – Cheapest since no redundancy, but high risk
- RAID 5 – Efficient use of drives with parity, but rebuild times are concerning
- RAID 10 – Fast and redundant, but high drive cost
- RAID 1 – Simple mirroring is affordable for 2-4 drives
For home NAS, RAID 1 provides the best balance of low cost with redundancy. RAID 5 offers efficient use of storage, but isn’t recommended for large consumer drives. Avoid RAID 0 since you can get redundancy with mirroring or parity.
Can you convert between RAID levels?
Most RAID controllers allow converting arrays from one level to another with a reconfiguration process. For example, changing from RAID 5 to RAID 10. Key considerations for RAID migration:
- May require adding or replacing drives to meet minimums for new level
- Data will need to be rebuilt to new layout, which takes time
- Risk of data loss if drive fails during conversion
It’s best to choose your intended RAID level upfront when possible. Changing levels on a live production system should be approached cautiously and avoided if the risks are too high.
Can you expand a RAID array?
Expanding or growing a RAID array is possible by adding more drives. The process depends on the RAID implementation:
- Hardware RAID – Add drives and expand volume through controller interface
- Software RAID – Manually add drives then expand filesystem
For hardware RAID, expanding online is simple. Software RAID expansion may require taking down the array to add drives. In either case, expanding RAID provides a convenient way to add more storage capacity.
Should you use SSD or HDD with RAID NAS?
NAS RAID arrays can be constructed from traditional hard disk drives (HDDs) or solid-state drives (SSDs). The medium you choose impacts performance and cost:
- HDD – Much lower cost per TB, better capacity options for NAS. But slower and higher failure rates.
- SSD – Faster performance, especially random I/O. But more expensive and limited capacities.
For most home and small business NAS, HDD arrays offer the best value. Use SSD for storage performance is critical – database servers, virtualization, etc. In a hybrid RAID approach, use SSD for caching to accelerate HDD arrays.
Does RAID protect against viruses or ransomware?
Unfortunately, RAID provides no protection against viruses, malware or ransomware attacks. These threats can still infect and corrupt data on RAID arrays.
RAID only protects against physical drive failures. It does not safeguard against logical errors, accidental deletion, file corruption, or malicious software. You still need traditional anti-virus tools and backups to guard against data loss from those risks.
Can you implement RAID on external drives?
External USB or Thunderbolt drives can be combined into a RAID array provided the enclosure supports it. There are a few options:
- Enclosures with built-in hardware RAID
- Multi-bay docks that connect drives to a RAID controller
- Software RAID spanned across external drives
External RAID provides a versatile way to create portable, high-capacity redundant storage. Just be cautious of potential performance bottlenecks over the external connectivity.
Conclusion
While NAS RAID brings benefits like increased redundancy and performance, it also adds cost and complexity. RAID may provide minimal advantages for consumer NAS devices used for backup or non-critical data. The importance of RAID grows for business-critical data that demands maximum uptime and reliability. Assess your specific storage needs and availability requirements to decide if RAID makes sense with your NAS deployment.