RAID technology uses a combination of one or more physical drives to create data redundancy and improve performance. From RAID 0 to RAID 10, multiple RAID levels provide different trade-offs between performance, data redundancy, and cost-effectiveness. This article explores RAID levels 0, 1, 5, 6, and 10, compares software vs hardware RAID implementations, and discusses RAID level advantages and disadvantages as well as their ideal use cases.
What is RAID Storage?
RAID (Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks) storage combines multiple disks to improve data reliability, performance, and ease-of-access of data. RAID storage provides data continuity for immediate data protection and recovery in case a drive fails. RAID storage is not a backup alternative because it does not protect against accidental deletion, malware infection, or natural disasters.
Primarily used for redundancy, RAID storage is designed to maximize uptime and data availability. RAID systems achieve this by employing multiple drives working in parallel. You’ll often see the following terms used when discussing RAID systems:
- RAID Level
There are multiple levels of RAID storage systems. The most used RAID levels are RAID 0, 1, 5, 6, and 10, each with its own advantages and disadvantages.
RAID Software vs Hardware
There are two ways to manage RAID arrays. One way is to use RAID software. In some cases, usually with lower-level RAID systems, a RAID driver built into a server’s operating system can be used to manage basic RAID configurations such as RAID levels 0, 1, and 10. However, RAID software increases overall processing loads on a server and could slow RAID calculations.
Another way to manage arrays is to use RAID hardware, where all the drives are connected to a hardware RAID controller. A hardware RAID controller can be on a separate RAID card or built into the computer’s motherboard and can also be attached to a different server. With a hardware RAID controller, the server processor is not subject to any additional load.
Hardware RAID is faster, and it’s easier to replace a failed drive, but it can be more expensive than software RAID.
Software RAID embeds disk controller software into the computer’s operating system and is typically less expensive than hardware RAID but can be slower and must be compatible with the associated operating system.
RAID Levels 0, 1, 5, 6, and 10
RAID is available in multiple levels, including RAID levels 0, 1, 5, 6, and 10. RAID levels use techniques called striping, mirroring, and parity, and in some cases, a combination of two, to create each level. Below is a breakdown of each RAID level and the technique or techniques used for each level.
RAID 0 (Striping)
Data is split evenly across two or more disks, without any parity information for redundancy, by dividing the body of data into blocks and distributing them across multiple storage devices. Writes data across several drives in sequence and improves performance by allowing parallel access to multiple drives.
RAID 1 (Mirroring)
By replicating a set of data onto two or more disks, it creates a mirror or exact copy that offers protection against a single disk failure.
RAID 5/6 (Striping + Distributed Parity)
Parity calculates data on two drives and stores the results on a third drive. After replacing a malfunctioning drive, the RAID controller restores the lost information using the data from the two surviving drives. When both striping and parity are used, the data is divided into segments and evenly distributed across three or more disks, while the corresponding parity information is stored across multiple disks.
RAID 10 (Mirroring + Striping)
Combines the techniques of mirroring and striping. The performance of data storage is enhanced by spreading data stripes across multiple disks, similar to the RAID 0 method. However, each striped set is also mirrored to provide redundancy and protection against data loss in the event of a drive failure. RAID 10 requires at least four drives to operate and provides both high performance and high data reliability.
Now that you have a basic understanding of the techniques used in RAID levels 0, 1, 5, 6, and 10, let’s dive deeper into each level and explore their advantages, disadvantages, and uses, starting with RAID level 0.
RAID Level 0
RAID 0 splits data into smaller groups and stores them in different disks (striping). RAID 0 provides unparalleled read/write speeds but lacks redundancy, resulting in the loss of all data within the array if one of the drives fails. To implement RAID 0, at least two drives are required.
RAID 0 has no overhead, is easy to implement, and is ideal for speed as it distributes data across the array, allowing for two more drives to work simultaneously while reducing latency.
Due to its lack of fault tolerance, RAID 0 is unsuitable for mission-critical systems as all of the storage capacity is utilized, leading to the loss of all data within the array if a single drive fails.
RAID 0 is best used for video editing or image retouching where speed and caching are required, but not data redundancy.
RAID Level 1
RAID 1 uses mirroring to store data by keeping a separate copy of the data on the remaining available disks (mirroring). In the event of a disk failure, the data remains accessible on the other disks, providing robust data protection. In addition, RAID 1 has the same speed as writing/reading to one disk and requires at least two drives.
RAID 1 is ideal for speed and has comparable performance to a single drive. Data simply needs to be copied to the replacement drive if a drive failure occurs.
RAID 1 has a storage capacity of only half as data is written twice. Additionally, it may not allow for a host swap of the failed drive, which means you'll need to power down the system before replacing the drive.
When data protection and availability are essential, RAID 1 is an excellent option for critical storage systems like accounting systems.
RAID Level 5
RAID 5 uses both striping and parity to provide a balance of speed and protection. Data is split into groups across all available drives, and distributed parity is created to allow the data on the other drives to reconstitute what was lost on a failed drive. RAID 5 requires a minimum of three drives, but it is possible to use up to 16 drives if needed. As a result, RAID 5 can maintain data integrity and accessibility in the event of a single drive failure.
RAID 5 is fast at reading data but can be slower when writing data. In the event of a drive malfunction, all data remains accessible. Failed drives can be hot-swapped, so there is no need to power down.
RAID 5 data restoration (rebuild time) may take longer depending on the size of the disk that needs to be restored. It also depends on the load on the array as well as the speed of the controller. If two drives fail, data is lost and decreased write performance is due to real-time parity calculations.
The security offered by RAID 5 is outstanding while its performance is decent. The best use is with a file server or large-capacity storage requirements.
RAID Level 6
RAID 6 uses striping and parity. RAID 6 uses double parity, which means two sets of parity data are calculated and stored across the drives in an array, allowing the array to reconstruct data even if two drives fail simultaneously. The two sets of parity data are calculated using different algorithms to ensure that they provide independent protection against drive failure. RAID 6 requires at least four drives.
RAID 6 provides fast data reading because data can be read from multiple drives simultaneously, which also improves fault tolerance. In case of a dual drive failure, data accessibility is maintained even during the replacement process. Can be hot-swapped for faster disk replacement – no downtime.
RAID 6 write speeds are slower than write speeds on a RAID 5 configuration. The reason is double parity, requiring additional calculations, whereas RAID 5 uses single parity.
RAID 6 combines optimal storage capacity, robust security, and satisfactory performance. Best for situations where data availability and fault tolerance are critical such as enterprise storage systems, database servers, storing large video files, etc.
RAID Level 10
RAID 10 uses both mirroring and striping. Combining RAID 1 and RAID 0, RAID level 10 is also known as a nested or hybrid RAID configuration, which mirrors all data on secondary drives. The RAID controller achieves redundancy by writing the same data on two or more drives, and it distributes data chunks across various drives using block-level striping. A minimum of four drives are required to accommodate both mirroring and striping techniques for data redundancy and performance improvement.
RAID 10 data rebuilding is fast since it uses mirroring, offering increased performance as you can read and write data simultaneously, making this a cost-effective solution.
Due to the allocation of half of the storage capacity for mirroring, RAID 10 has a high overhead, and the loss of two drives in the same mirrored pair results in data loss.
RAID 10 is best for I/O-intensive applications such as databases, email and web servers, and any operations that require high disk performance.
The selection between software and hardware RAID depends on various factors such as budget and system requirements, as RAID technology provides multiple data storage and protection options. Each RAID level has its unique advantages and disadvantages concerning performance, data protection, and cost, so the best RAID solution ultimately depends on individual needs and priorities. It's crucial to remember that RAID is not a substitute for backups, does not guarantee 100% uptime, and does not provide protection against human error, data corruption, or security issues.
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