What Is RAID? Pros and Cons of 10 RAID Levels Explained
Every year the data we create increases dramatically—from 4K movies and digital games to creative projects and everyday files—all of them take up significant storage space. Simply adding more hard disks often result in scattered data and lacks proper security: if one disk fails, years of files could be lost.
This is where RAID steps in. By combining multiple drives into one system, RAID delivers both performance and protection, transforming ordinary disks into smarter, more reliable storage. RAID is a fundamental feature in most NAS (Network Attached Storage) devices, which use different RAID levels to give users larger capacity, better speed, and stronger data safety in a centralised storage device.
In this guide, we’ll explain what RAID is, explore different RAID levels, and highlight the pros and cons of each configuration to make it easier to choose the right setup.
RAID Basics
What Is RAID?
RAID (Redundant Array of Independent Disks) is formed by combining multiple independent disks into a single disk group. Depending on the RAID level, it can increase usable capacity, improve performance through striping, or enhance fault tolerance with mirroring or parity.
RAID is not a single configuration—it comes in different forms, each with its own pros and cons. Depending on the level, RAID can improve speed, increase data safety, or make storage more efficient. Common RAID levels include RAID 0, RAID 1, RAID 5, RAID 6, and RAID 10, with some designed for performance, others for protection, and some aiming to balance both.
RAID uses three main techniques to manage data:
- Striping spreads data across multiple disks, which boosts read and write speeds but does not protect against disk failure.
- Mirroring copies data exactly onto two or more disks, providing strong protection if a disk fails, but it uses more storage space.
- Parity adds extra information to help rebuild data if a disk fails, offering a balance between storage efficiency and fault tolerance.
RAID Configurations
Hardware RAID
Hardware RAID uses a dedicated controller card to manage multiple disks. This controller has its own processor and memory, which handles data operations without relying on the computer’s CPU. Many enterprise environments choose hardware RAID for mission-critical tasks . These setups often include features like battery-backed cache and advanced error handling.
Advantages :
Offloads RAID processing from the host CPU, improving overall system speed.
Offers better performance, especially for databases and high IOPS workloads.
Provides advanced features such as write-back caching and instant failover.
Easier disk replacement due to independent controllers.
Disadvantages :
Higher upfront cost because of the need for specialized hardware.
Replacement or upgrade can be complex if the controller fails.
Strict compatibility requirements for drives and components.
Hardware RAID is ideal for large-scale storage, financial services, healthcare, and environments where data integrity and speed matter most.
Software RAID
Software RAID uses the operating system to manage disk arrays. It does not need extra hardware, making it a popular choice for home users and small businesses. Many operating systems, like Linux, Windows, and macOS, offer built-in RAID support.
Advantages :
Cost-effective, no need for dedicated hardware.
Flexible, works with different drive types and sizes.
Easy to update and add new features through software.
Disadvantages :
Uses the host CPU and RAM, which can slow down other tasks.
Performance may drop during heavy workloads.
Recovery and migration can be complicated due to OS dependencies.
RAID Levels
The RAID levels start at RAID 0 and continue through several variations, each created for a different balance of performance and protection.
RAID 0
RAID 0, also known as Stripe or Striping, is the highest read and write performance among common RAID levels. It stripes data across two or more disks, dividing files into blocks and writing them simultaneously. This method maximizes usable capacity and delivers very high read and write performance—at least in theory, speeds can scale with the number of disks; however, in practice, they are limited by factors such as seek time and controller efficiency.
Pros:
- Simple setup.
- Greatest speed and capacity.
- Low cost.
Cons:
- No data redundancy.
- Failure of any disk causes total data loss.
Ideal Use Cases:
- Video editing scratch disks.
- Gaming systems.
- Temporary storage where speed matters and data can be easily replaced.
However, RAID 0 has a clear drawback—there is no redundancy. If a single disk fails, all of the data in the array is lost and unrecoverable. For this reason, RAID 0 is best suited for cases where speed is more important than safety, such as temporary storage, gaming, or scratch disks. It is not recommended for storing important or irreplaceable data.
RAID 1
RAID 1 is also known as Mirroring, and its core purpose is to maximize the availability and recoverability of user data. By writing the same data to two disks at the same time, when one disk fails, the complete data on the other disk can ensure the normal operation of the system and the recovery of data, providing a high level of data redundancy.
Aspect |
Details |
|---|---|
Main Characteristics |
Mirroring; identical data on each disk . Volume size equals the smallest disk. Functions as long as one drive is active. |
Pros |
Fault tolerance; improved read performance ; easy to configure. |
Cons |
Uses only 50% of total storage ; higher cost; requires system shutdown to replace drives in software RAID. |
Another advantage of RAID 1 is its ability to rebuild automatically. When a failed disk is replaced, the array restores the missing data to the new disk by copying it from the healthy one. However, this process requires at least one disk to remain intact, and rebuilding may temporarily reduce system performance.
The main drawbacks of RAID 1 (mirroring) are its low storage efficiency (the actual usable capacity is only half of the total disk capacity), high construction cost (requiring twice the disk space to store the same data), and limited improvement in write performance. Despite the fact that RAID 1 provides high data security, its low storage efficiency and cost issues limit its application, and it cannot replace the importance of off-site backups.
In many respects, RAID 0 and RAID 1 are opposites—RAID 0 provides the quickest performance without protection, while RAID 1 offers maximum protection but at the cost of efficiency. For those who want a balance between speed, capacity, and protection, more advanced RAID levels such as RAID 5 or RAID 6 may be a better fit.
RAID 2 and RAID 3 and RAID 4
RAID 2, RAID 3, and RAID 4 are rarely used today . RAID 2 relies on complex hardware and error correction codes, making it expensive and obsolete. RAID 3 and RAID 4 use a dedicated parity disk, which creates a bottleneck during write operations. These levels struggle with small, random I/O and have limited scalability.
RAID 2 requires specialized controllers and is no longer implemented.
RAID 3 and RAID 4 suffer from poor write performance due to a single parity disk .
Modern systems favor RAID 5 and RAID 6 for better performance and reliability.
RAID 5 and RAID 6
RAID 5
RAID 5 and RAID 6 are two widely RAID levels. RAID 5 is a disk redundancy array technology that requires a minimum of three hard disks. It uses distributed parity, spreading both data and parity information across all disks. This design eliminates the bottleneck of a dedicated parity disk, offering both improved performance and enhanced fault tolerance. Its advantage is that when one disk fails, the system can use the data and parity information from the remaining disks to recalculate and reconstruct the missing blocks, thus restoring data and ensuring availability.
RAID 5 is quite similar to RAID 3. It can be seen as an improvement. RAID 3 uses a dedicated disk to store parity information. This approach provides redundancy and fault tolerance but creates a performance bottleneck. RAID 5 avoids this issue by distributing parity across all disks.
RAID 5 also has drawbacks. Write performance is slower compared to RAID 0 or RAID 10 because each write requires parity calculation. In addition, rebuilding after a disk failure can take a long time and is stressful for the remaining drives. This increases the risk of a second failure during recovery.
Aspect |
RAID 5 |
RAID 6 |
|---|---|---|
Fault Tolerance |
Can tolerate failure of up to 2 disks |
|
Write Performance |
Slower due to parity calculation |
Slower than RAID 5 because of double parity |
Read Performance |
Fast due to striping across disks |
Fast due to striping across disks |
Storage Efficiency |
Higher storage efficiency |
Lower storage efficiency due to extra parity |
RAID 6
RAID 6 is built on RAID 5 and was designed to improve data protection and even more, essentially as an extension of the RAID 5 level. The main difference from RAID 5 is that RAID 6 adds a second independent parity block (known as “P” and “Q” dual parity), which enhances fault tolerance.
RAID 6, through distributing data and two independent parity blocks, can maintain data integrity and security even if two physical disks fail, providing stronger fault tolerance than RAID 5. However, if two disks fail, the array will enter a degraded mode, resulting in reduced performance. Its downside is that write performance is relatively lower, since it requires calculating and writing two parity blocks, and usable storage capacity is reduced. RAID 6 is suitable for scenarios with extremely high requirements for data security, such as large databases and data centers.
Overall, RAID 5 fits general-purpose NAS, media storage, and backups where moderate fault tolerance is acceptable. RAID 6 is preferred for enterprise storage, large databases, and archival systems where maximum data protection is required.
Hybrid RAID
In addition to the basic RAID levels such as RAID 0, 1, 2, 3, 4, 5, and 6, there are also hybrid, or nested, RAID levels that combine two types to balance performance and redundancy.
RAID 10, RAID 50 and RAID 60
RAID 10 (1+0) is the most common hybrid RAID and requires at least four disks and offers both speed and fault tolerance by mirroring and striping.
RAID 50 (5+0) uses a minimum of six disks, striping across multiple RAID 5 groups to improve throughput while still tolerating one disk failure per group.
RAID 60 (6+0), which needs at least eight disks, stripes across multiple RAID 6 arrays, providing stronger protection by surviving two disk failures per group, though with lower write performance and efficiency.
RAID Level |
Combination |
Performance |
Redundancy |
Key Benefits |
Trade-offs |
|---|---|---|---|---|---|
Mirroring + Striping |
High read/write speeds |
Data mirrored for fault tolerance |
Fast recovery, high speed |
50% disk space efficiency |
|
RAID 01 |
Mirrored striped sets |
Fast performance |
Data available as long as one group is operational |
Survives group failure |
Limited usable capacity |
RAID 50 |
RAID 5 arrays striped |
Enhanced write speed |
Multiple disk failures tolerated |
High recovery speed |
Higher cost |
RAID 60 |
RAID 6 arrays striped |
Improved transfer/read speeds |
Multiple simultaneous failures tolerated |
High fail-safe |
Lower write IOPS, less space efficiency |
In short, RAID 10 is ideal for animation, rendering, and high I/O workloads . RAID 50 and RAID 60 suit large NAS environments needing both speed and redundancy .
Choosing RAID
Factors AND Use Cases
Selecting the right RAID level depends on several important factors. Each environment has unique needs, so users should weigh these elements carefully:
Drive Count : The number of available disks limits which RAID levels can be used. For example, RAID 10 needs at least four drives , while RAID 5 requires three. More drives can increase storage capacity or redundancy.
Fault Tolerance : Some RAID levels, such as RAID 1, 5, 6, and 10, offer protection against disk failure. RAID 0 and JBOD do not provide any redundancy, so data loss is possible if a drive fails.
Performance : Speed requirements vary by application. RAID 0 delivers the fastest performance but lacks data protection. RAID 10 combines speed and fault tolerance, making it suitable for critical workloads. RAID 5 and 6 balance speed and redundancy but have slower write speeds due to parity calculations.
Storage Efficiency : Usable storage depends on the RAID type. Mirroring, as in RAID 1 and 10, reduces available space, while striping maximizes it.
Budget : Higher fault tolerance and performance often require more drives, increasing costs. RAID 10 offers fast rebuilds and reliability but costs more than RAID 5 or 6.
Tip: RAID improves data safety and speed, but it does not replace regular backups . Data corruption or accidental deletion can still affect all drives in the array.
Influence on RAID Selection |
|
|---|---|
Drive Count |
Minimum number of disks required varies; more disks can increase capacity or redundancy. |
Fault Tolerance |
Higher levels offer better protection; some provide none. |
Performance |
Varies by RAID type; some focus on speed, others on safety. |
Budget |
More drives and higher performance increase costs. |
Different use cases call for different RAID levels. For example, video editors may choose RAID 0 for speed, while businesses needing data protection may select RAID 5, 6, or 10.
UnifyDrive UT2 Features
Supported RAID Modes
UnifyDrive UT2 gives users flexible storage options with support for RAID 1 and its unique UDR mode. These modes allow users to balance redundancy and usability based on their needs. RAID 1 mirrors data, providing strong protection against drive failure. UDR mode offers a blend of usability and redundancy, which helps safeguard large media projects while minimizing downtime.
UnifyDrive UT2’s RAID1 and UDR modes protect creative professionals from data loss. These modes ensure that video editors and studio teams can work efficiently, even during critical workflows.
UnifyDrive UT2 offers creative professionals and travelers a portable, secure, and intelligent storage solution.
Final Thoughts
In this article, we introduced different RAID configurations and outlined their respective advantages and disadvantages. Understanding RAID configurations can help you make more informed decisions when choosing a NAS, ensuring that your setup matches your specific needs for data protection and ease of use.
