RAID, also known as redundant array of independent disks or redundant array of inexpensive disks, utilize multiple hard drives to bolster data backup and preservation. Most RAID configurations use different techniques, like mirroring, striping, or parity, to ensure system efficiency and integrity.

In modern computing, the standard RAID levels include:

• RAID 0: Data striping
• RAID 1: Disk mirroring
• RAID 2: Bit-level data striping with Hamming-Code parity
• RAID 3: Bit-level data striping with dedicated parity
• RAID 4: Block-level striping with dedicated parity
• RAID 5: Data striping with parity
• RAID 6: Data striping with double parity

While these configurations cover all of the basic RAID scenarios, there are some more advanced use cases, too. Some of these scenarios require a nestled or non-standard RAID configuration.

Nested RAID Levels
Sometimes referred to as hybrid RAID, the typical nested RAID configuration combines two or more standardized RAID levels into one package. Depending on the RAID levels you choose, your system might benefit from increased performance, greater data redundancy, or improved data integrity.

The most popular nested RAID configurations in modern computing include:

• RAID 01: Data striping and disk mirroring
• RAID 03: Byte-level data striping and a dedicated parity
• RAID 10: Block-level data striping and disk mirroring
• RAID 50: Block-level data striping and distributed parity
• RAID 60: Block-level striping and dual parity
• RAID 100: A stripe of RAID 10s

As you can see, the combined usage of one or more RAID levels can be greatly beneficial to a modern system. However, nested RAID still uses the fundamental functionality of the standard RAID levels. What if you want to explore RAID beyond the default or standard levels?

Non-Standard RAID Levels
In some cases- non-standard RAID levels are used. Many non-standard RAID levels were developed by individual manufacturers for use in their products, and some are only designed to work with specific system specifications. Others are implemented as needed - regardless of the system, products, or devices used.

• RAID 1E: Striped mirroring
• RAID 5E: RAID 5 implementation with a hot spare drive
• RAID 5EE: RAID 5 implementation with a hot spare drive that is integrated into the data striping set
• RAID 6E: RAID 6 implementation with a hot spare drive that is active in the block rotation scheme

There are other forms of non-standard RAID, too. For example, RAID-DP uses double-parity disk protection to help prevent disk errors and data corruption. RAID Z was designed by the Sun Company specifically for use with the ZFS file system, and Linux MD RAID 10 only works on Linux-based operating systems. Since manufacturers and developers are free to create their own configurations to meet specialty needs, the possibilities are nearly endless.

Making RAID Work for You
The key with RAID finding the configuration that works best for you and your needs - whether that’s standard, nested, or non-standard RAID. With plenty of options to choose from, you’re sure to find that perfect configuration sooner or later.

You may read more about non-standard and nested RAID levels in Wikipedia: Non-standard RAID levels and Nested RAID levels.