RAID stands for “Redundant Array of Independent Disks”. It is a data storage technology that combines multiple disk drive components into a logical unit for the purposes of data redundancy, performance improvement, or both [1].
The concept of RAID was first outlined in 1987 by researchers from the University of California, Berkeley. The different RAID levels were created to provide various combinations of increased data reliability and/or increased input/output performance. For example, some RAID levels focus on increased data protection through mirroring, while others use striping methods to enhance performance [2].
There are several standard architectures or RAID levels, which each have their own benefits in terms of redundancy and/or performance. The most common levels include RAID 0, RAID 1, RAID 5, and RAID 10. We will explore the differences between these levels next.
RAID 0
RAID 0, also known as disk striping, is a RAID configuration that provides improved performance but no redundancy. In RAID 0, data is split across multiple drives in chunks called stripes. The stripes from each drive are interleaved, so sequential data blocks are spread across multiple disks.
The main benefit of RAID 0 is increased input/output performance. By spreading data across multiple disks, multiple disk heads can read and write data in parallel, greatly increasing transfer speeds. However, RAID 0 provides no data protection or fault tolerance. If one disk fails, all data across the entire array will be lost. Therefore, RAID 0 is typically used in non-critical storage environments where performance is valued above fault tolerance, such as gaming systems or video editing workstations. RAID 0 is also sometimes used for cache or scratch disks that only contain temporary data.
Overall, RAID 0 allows you to combine multiple physical disks into one large logical drive for enhanced performance. But the tradeoff is complete lack of redundancy. With no built-in resilience against disk failure, RAID 0 should not be used for mission critical data or applications requiring high availability.
Sources:
https://iboysoft.com/wiki/raid.html
https://tech-latest.com/raid-0-1-5-10-easy-explanation/
RAID 1
RAID 1, also known as disk mirroring, is a RAID configuration that provides redundancy by duplicating all data from one disk to a second disk (CCTV DVR with RAID Hard Drive Backup, 2019). This mirroring protects data in the event one of the disks fails. With RAID 1, data can be accessed from either disk which provides improved performance for read operations. However, write performance is not improved as all writes must be completed to both disks. The minimum number of disks required for RAID 1 is 2.
A key advantage of RAID 1 is that it provides full redundancy. If one disk fails, the data is fully intact and accessible on the second disk. This protects against data loss in the event of a single disk failure. The disadvantage is that RAID 1 results in 50% storage efficiency since the available capacity is equivalent to a single disk. For optimal redundancy, the disks should be the same size.
RAID 5
RAID 5 is a common RAID level that offers a good balance between redundancy and performance. RAID 5 uses striping with distributed parity, which means the data is striped across multiple drives just like in RAID 0, but parity information is also distributed across the drives (Source). The parity information allows for data recovery if one of the drives fails. Specifically, the distributed parity scheme works as follows:
Data is split into blocks and striped across the drives. For each set of blocks, one block per drive is reserved for parity information. The parity block is calculated by XORing the data blocks in the set. If any single drive fails, the data on the failed drive can be recreated by XORing the data blocks and parity blocks on the remaining drives. This provides redundancy while still allowing multiple drives to be used in parallel for performance.
RAID 5 requires a minimum of 3 drives, but commonly 4+ drives are used. It provides good performance and the ability to recover from a single drive failure. However, recovering from a second drive failure is not possible with RAID 5 (Source). Overall, RAID 5 offers a good combination of performance, capacity and redundancy for many applications.
RAID 6
RAID 6 is a type of RAID that offers high redundancy for data protection by using double distributed parity. This means RAID 6 stripes data and parity information across all the disks in the array and uses two separate parity schemes to provide fault tolerance against up to two disk failures.
The double distributed parity provides an extra layer of protection compared to RAID 5, which only has single parity. If one disk fails in a RAID 6 array, the data can still be reconstructed using parity information. If a second disk fails before the first failed disk has been replaced, RAID 6 can still recover all data using the second parity scheme.
Because of the dual parity, RAID 6 requires a minimum of four disks. The tradeoff is you lose more total capacity to redundancy compared to RAID 5. However, for mission critical data where uptime and data protection are paramount, the advantages of RAID 6 often outweigh the capacity loss.
Overall, RAID 6 is commonly used in environments that demand high availability and fault tolerance, such as servers, large databases, and enterprise storage systems. The dual parity provides excellent protection against multiple disk failures.
Source: http://hitachistoragefornew.blogspot.com/2016/06/raid.html
RAID 10
RAID 10, also known as RAID 1+0 or striped mirror, combines the techniques of RAID 0 (striping) and RAID 1 (mirroring) to provide faster performance and better redundancy compared to either RAID 0 or RAID 1 alone. With RAID 10, data is striped across mirrored pairs of drives. This means data is broken up and written in parallel across two drives at the same time. Then, this striped set is mirrored onto another set of drives.
The key benefit of RAID 10 is increased I/O performance combined with fault tolerance. By striping data across multiple drives, RAID 10 enables fast read and write speeds. The mirrored copies provide fault tolerance by maintaining two complete copies of all data. If one drive fails, the mirrored copy ensures continued access to data.
RAID 10 requires a minimum of 4 drives and an even number of drives. At least 50% of total capacity is needed for redundancy. The I/O performance of RAID 10 increases with more drives, making it well-suited for write-intensive applications that need faster speeds.
Hardware vs Software RAID
RAID can be implemented using dedicated hardware RAID controllers or through software RAID using the operating system. Both options have their pros and cons.
Hardware RAID uses a dedicated RAID controller card that handles all RAID calculations and processes. The main advantages of hardware RAID include:
- Better performance, especially for write operations
- Less impact on CPU usage
- Option for battery-backed cache to protect data in case of power loss
The downsides of hardware RAID include:
- More expensive since it requires purchasing a RAID controller
- Less flexibility if you need to change your RAID level
- Vendor lock-in makes it harder to migrate RAID arrays to new systems
Software RAID runs the RAID calculations on the CPU and leverages the operating system’s software drivers. Benefits of software RAID include:
- Lower cost since it doesn’t require additional hardware
- More flexibility to change RAID levels
- Easier to migrate RAID arrays to new systems
Downsides of software RAID include:
- Slower performance compared to hardware, especially for write operations
- Uses CPU resources that could impact performance of other processes
- No battery-backed cache option
Overall, hardware RAID is preferred for performance-critical applications that demand faster write speeds. Software RAID provides a more flexible and cheaper option for less demanding workloads.
Choosing a RAID Level
When selecting a RAID level, there are several factors to consider:
- Performance – Some RAID levels like RAID 0 offer better read/write performance while others like RAID 1 focus more on redundancy and reliability.
- Redundancy – RAID levels like RAID 1, 5, 6, and 10 provide varying levels of redundancy in case of drive failure. RAID 0 has no redundancy.
- Capacity – RAID 0 provides full additive capacity of the drives. RAID 1 cuts capacity in half. RAID 5/6 have less loss than RAID 1. RAID 10 capacity depends on the setup.
- Number of drives – Some RAID levels like RAID 10 require a minimum of 4 drives while RAID 1 needs at least 2 drives.
- Cost – Adding more drives or redundancy increases cost. RAID 1 and 10 are more expensive than RAID 5 or 6 for large arrays.
- Type of storage media – Some RAID levels work better with SSDs vs HDDs.
- Ease of setup – RAID levels like RAID 0 are easier to setup than complex RAID levels like 6.
Understanding the strengths and weaknesses of each RAID level based on these factors allows selecting the right RAID for your needs.
Implementing RAID in Windows 10
Setting up RAID in Windows 10 is fairly straightforward using the built-in Storage Spaces feature. Here are the steps to configure RAID:
- Open Windows Settings and go to System > Storage.
- Click on “Storage Spaces” in the left sidebar.
- Click on “Create a new pool and storage space.”
- Choose your physical disks to include in the RAID array.
- Select the RAID level you want, such as Mirror, Parity, or Striped.
- Specify the size of the storage pool.
- Give the storage pool a name and description.
- Click “Create pool” to initialize the RAID array.
Once created, the RAID storage pool will appear in File Explorer like any other drive for storing files normally. You can monitor or manage the pool under the Storage Spaces settings.
For additional details, refer to this HP guide on step-by-step RAID setup in Windows 10.
Conclusion
In summary, RAID (Redundant Array of Independent Disks) allows multiple physical disks to be used together as one or more logical units. The different RAID levels provide various combinations of increased data reliability, better performance, or increased usable disk space.
Some key benefits of using RAID include:
- Improved performance – By spreading data across multiple disks, RAID can improve read and write speeds.
- Increased capacity – RAID levels like 0, 5, 6 and 10 allow multiple disks to be combined into larger logical volumes.
- Redundancy/fault tolerance – RAID provides protection against disk failures. If one disk fails, the data can be rebuilt from the remaining disks.
- Ease of use – RAID presents multiple physical disks to the operating system as standard logical volumes.
Overall, implementing RAID allows organizations to optimize their storage environment for performance, capacity and reliability. Carefully choosing the appropriate RAID level based on business needs is key to maximizing the benefits.