What is Raid and what are its various types?

What are Raid and its various types? “RAID” (“Redundant Array of Independent Disks,” sometimes referred to as “Redundant Array of Inexpensive Disks”) is a storage virtualization technology that integrates several disk drives into logical components to provide redundancy of data, performance improvement, or both. 

This is the opposite of the old idea of high-quality mainframe disk drives, referred to as “single big cost disk” or SLED.

What exactly is Raid? What are the different types of it?

Data is spread across drives in various methods, known by the RAID level, based on the amount of redundancy and the performance. The various schemes or layouts for the distribution of data are identified by the term “RAID” and followed by numbers. For instance, RAID 1 or RAID 2. 

Each scheme, as well as RAID level, has various levels of balance between the primary goals of availability, reliability performance, and capacity. RAID levels that are higher than RAID 0 protect unrecoverable sector read mistakes and against the possibility of failures of all physical drives.


A number of RAID levels use an error-proofing scheme known as “parity,” which is an extremely popular method used in the field of information technology. It provides fault tolerance for a particular collection of data. 

Numerous RAID levels use basic XOR. However, RAID 6 uses two separate parties that are based on the multiplication and addition in the specific Reed–Solomon error correction or Galois field.

RAID can also offer the security of data using Solid-state drives (SSDs) with no cost of a complete SSD system. For instance, a speedy SSD could be mirrored using an electronic drive. To provide the fastest possible speed, the right controller is needed that utilizes the fast SSD for each read operation. It’s called “hybrid RAID.”

Standard Levels

At first, there were five levels of RAID. Since then, numerous variations have developed with several levels nested as well as a number of levels that are not standard (mostly exclusive). RAID levels, as well as their associated formats for data, can be standardized through the Storage Networking Industry Association (SNIA) in the Common RAID DDF PDisk Drive Format) standard:


It is a form of striping. However, there is no mirroring or even parity. In comparison to a spanned volume, the capacity of its volume is exactly the same. It’s the total capacity of the drives within the set. However, since striping spreads the contents of every file to all drives of the set, failure of any drive can cause the entire files or volume to go missing. 

In contrast to the case of spanned volumes, they preserve the files that are on the non-failing drives. The advantage is that the speed of reading and writing operations to any particular file will be increased by the number of drives. Unlike spanned volumes, the reading and writing operations are carried out simultaneously.


RAID 1 consists of data mirroring but no stripping or parity. Data is written in a similar manner to multiple drives, which results in the “mirrored collection” comprising drives. 

This means that every read request is handled by any drive in the set. If the request is sent to all drives in the collection, then it could be served through the one that is able to access initially (depending on its rotational latency), which improves the performance. 

The sustained read throughput, provided that the controller or program is optimized for it, is similar to the total throughput of each drive within the set, exactly like the previous level. The actual read-throughput of many RAID 1 implementations is slower in contrast to the most powerful drive. 

The write throughput is generally slower as every drive needs to be upgraded, and the one with the lowest speed restricts the write speed. The array will continue to function for as long as a minimum of one drive is operating.


RAID 2 consists of bit-level striping that is based on Hamming-code parity. Every disk spindle’s rotation is synchronized, and data is divided so that every sequential bit is stored on one drive. Hamming-code parity can be calculated across identical bits and is kept on at least one drive for parity.

This is of historical importance only. Even though it was used on certain older machines (for instance, that of the Thinking Machines CM-2), at the time of writing, it’s not being used in any system that is commercially available.


RAID 3 is a byte-level striping that is dedicated to parity. Every disk spindle’s rotation is synchronized. Data is split so that each sequential byte is located on an entirely different drive. Parity is calculated over identical bytes and stored on a separate parity drive. RAID 3 is not widely used in the real world, but implementations exist.


RAID 4 consists of block-level striping with dedicated parity. This was previously utilized by NetApp but is now vastly replaced by a private version of RAID 4 that has two parity disks, known as RAID-DP. 

The primary benefit for RAID 4 over RAID 2 and 3 is the parallelization of I/O. That is, In RAID 2 and 3, the single read I/O operation involves reading the entire array of data drives; however, with RAID 4, one I/O read operation does not need to be distributed across all drives. In turn, there is a greater number of I/O processes that can be carried out in parallel, which improves the efficiency of smaller transfers.


RAID 5 comprises block-level striping that has distributed parity. In contrast to RAID 4, parity information is shared across the drives, which requires every drive, minus one, to be in operation. If a single drives, future reads could be calculated using the distributed parity to ensure that data cannot be lost. RAID 5 requires at least three disks. 

Similar to all single-parity ideas, massive RAID 5 implementations are susceptible to system malfunctions. The reason for this is trends in the time required to rebuild an array and the possibility of failure of drives in the process of rebuilding. Rebuilding an array involves the use of all disks to read data which could lead to another drive failure and even the destruction of all arrays. 

RAID 6 comprises block-level striping, which has double distribution parity. Double parity gives the ability to tolerate faults up to 2 failed drives. This means that the larger RAID groups are more feasible, particularly in high-availability systems, because larger capacity drives can take longer to repair.


RAID 6 requires at least four disks. Like RAID 5, a single drive failure can result in a decrease in performance for the entire array until it is replaced. By utilizing drives from different sources, it is possible to alleviate the most common issues related to RAID 5. The bigger the capacity of the drive and the bigger number of arrays, the less vital it becomes to pick RAID 6.

Software RAID

It’s crucial to understand that a RAID controller is the center part of a RAID system. It plays an essential function in the distribution of data among RAID disk arrays that include each Hardware RAID and Software RAID.

Software RAID utilizes the capabilities provided by software RAID. It is the RAID software or RAID driver that is built into the operating system of servers. This method doesn’t require additional hardware in order to link storage devices. It could, however, add to the overall processing load on servers and could result in slow RAID calculations and other functions that run by the gadget.

Many server operating systems are able to support RAID configurations, such as those that are from Microsoft, Apple, and various versions of Unix/Linux systems. Most of the time, Software RAID depends on the operating system utilized. Therefore it is not advised for divisions that are shared between several operating systems.


  • We can create a RAID configuration for the same operating system (e.g., Ubuntu) and then apply it to other similar systems.
  • Installation of software RAID is cost-effective since it does not require any additional hardware equipment.
  • Re-configuration of RAID levels is possible because the configurations are flexible and not complex.
  • Most operating systems are compatible with RAID Software configurations which makes it easier to install and complete configuration tasks that help solve various issues.
  • Software RAID is mostly suitable for processing basic RAID 0, 1, and 10 that do not create additional load on the system.


  • System failures on servers could have a negative effect on the integrity of data.
  • Software RAID implementation isn’t beneficial if there are several drivers on the system since certain conflicts may occur.
  • Certain operating systems only support certain ranges of RAID.
  • Software RAID has the potential to significantly impact the system’s load when making a complex RAID configuration.
  • There isn’t much opportunity to utilize RAID on an operating system that is clustered.
  • Repairing a failed disk could be complex.
  • Software RAID is susceptible to malware and viruses since it runs within the operating system of the server that is used for primary servers.

We’re looking into Software RAID and some of its strengths and weaknesses. We can conclude that this approach can be utilized for small projects with limited budgets and for situations where power-efficient computing and data security. Disk recovery and fast data aren’t top priorities.

It’s vital to be aware that these are just general suggestions as the options depend on the needs of the project and the work needed to be completed.

Hardware RAID

Hardware RAID is that all drives connect to the hardware RAID controller that is located on an individual RAID card or server or integrated into the motherboard. Hardware RAID controllers manage setups and RAID arrays. It can support multiple levels of RAID. 

In certain situations, the RAID controller may function as a miniature version of computers. It’s so because they are equipped with processors specifically designed to complete their work.

In the Hardware RAID installation, drives connect directly to each other via the RAID controller board. This is not limited to big servers but also to desktop computers. Processing Hardware RAID is a reference to separate controllers (such as ATA RAID, SATA, DELTA PLCetc.) at the storage system.

Since the RAID is controlled by and processed by the controller’s board, there’s no extra load for the processor of the server. Hardware RAID can also provide several other additional functions like the option of swapping disks in case of a single disk failure. In addition, Hardware RAID is more expensive than software RAID, but it is more efficient and has better functional compatibility.


  • It is easy to move the box around between servers, computers, and OS.
  • A high level of system efficiency is crucial for older systems that are unable to boost the computing power of computers.
  • The protection against data corruption and loss could occur in case of a power interruption during the production of backup copies as hardware RAID makes use of backup batteries and its internal flash memory.
  • There are fewer problems when using RAID systems in the process of creating backup copies as well as data recovery.
  • Hardware RAID uses its cache-memory memory for creating backup copies and data recovery.
  • The flexibility to configure RAID that is difficult to achieve without the right equipment.
  • Further RAID levels can be utilized, but they will require greater resources.
  • It works well on all kinds of disks.
  • Compatibility with a variety of OS.


  • It is also more costly as it requires more equipment.
  • An interesting thing is Hardware RAID can have a lower efficiency ratio for certain projects and tasks, considering its cost.
  • When the RAID controller fails, It must be replaced by a replacement model to prevent malfunction. If a replacement controller isn’t available immediately, system performance delays could be experienced.
  • With Hardware RAID, it is possible to encounter difficulties when installing HDDs from different manufacturers or the installation of SSD and HDD drives.

In analyzing the advantages/disadvantages of Hardware RAID, we see it is a viable option to help with more expensive projects that don’t have budget limitations. Additionally, it’s an ideal option when the security of data and the power of computing are essential. In some instances, Hardware RAID can be better suited to projects that are connected to technical devices since interaction with storage devices may cause problems.

Hybrid RAID

In certain instances, it’s possible that a Hybrid RAID offering may be better. For instance, if it’s the case that RAID can be integrated with the motherboard’s BIOS, it could provide additional redundant data when the system is powered on and could help stop data corruption.


  • In many instances, Hybrid RAID systems are equipped with a graphic user interface that can be used to assist with the RAID configuration.
  • Hybrid RAID costs little and is ideal for a variety of projects.
  • Hybrid RAID is typically able to function on multiple systems that run the same operating system.
  • Hybrid RAID may protect against the boot system failing during boot, which could be caused by a system error or similar failures.


  • There are also issues concerning drive swaps as well as data recovery.
  • A hybrid RAID could cause excessive load on servers that can affect productivity.
  • Some operating systems (especially the latest ones) may require drivers for RAID to be upgraded regularly. This could cause driver conflicts.
  • Since software RAID is susceptible to viruses, it could have a less-secure threat model.

Hybrid RAID is, however, an excellent choice, but it can have some peculiarities. This is why it’s ideal for a variety of projects. It is recommended to select the Hybrid RAID if you know beforehand what issues could arise and the best ways to resolve these issues.

Additionally, it could be an ideal choice if your project requires both Software and Hardware RAID. But, these projects are typically very specific. In the end, it’s vital to remember that the final decision will be based solely on your project’s unique goals and requirements.

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