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What is RAID (Redundant Array of Independent Disks)?

RAID technology presents ways of combining or grouping disk drives to provide greater capacity, performance,and reliability than would otherwise be offered by a single disk. It’s an excellent (and proven) way to protect large amounts of data while providing outstanding performance and capacity.

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What are RAID levels?  

There are several ways that disks can be combined into an array. RAID levels describe these various ways. Each level has specific benefits (and possible drawbacks). Selecting which RAID level is best for you depends upon your application and which benefits will serve your needs best.

Note that not all RAID levels provide data protection. RAID level 0, for example, is an excellent way to combine disks within an array for maximum speed and capacity. But RAID level 0 doesn’t protect data from a disk failure. Applications, such as video editing projects, often require the extremely high data transfer rates that only RAID level 0 can provide. These ‘performance driven’ applications must rely on other forms of backup for data protection. Thus, RAID 0 is recommended only when data loss would be inconvenient, but not catastrophic. Video and audio applications, for example, typically have their source data on tape. They also output (or master) to tape or DVD, which can serve as its own form of backup.

Other RAID levels, such as 1, 5, and 10, are specifically designed to protect all of the data on an array - even if a disk fails! For mission critical applications, where data protection is vital, selecting storage systems supporting at least one of these RAID levels is essential.

NCS offers storage products that support RAID levels 0, 1, 5 and 10. Following are brief descriptions of each of these levels. Additional information can be provided by your Ncs representative. They can also help you select a storage system and RAID level that best suits your application.

RAID Level 0 / RAID Level 1 / RAID Level 5 / RAID Level 10 

RAID Level 0

All of the disks within an array are combined for maximum speed and capacity. Data stored to the array is divided into equal parts and transferred in parallel to all of its disks at the same time. This accounts for this level’s very high performance.

RAID 0 is typically the fastest RAID level defined. It’s primarily benefit is speed and it does NOT offer data protection. Keep this in mind when selecting it for your application.

RAID Level 1

The disks within an array are divided into two equal sets. Data stored to the array is replicated (without compression) and stored on each set, resulting in two copies of your data at all times. Thus, if a disk should fail within either set, the storage system will continue transferring data normally - but using only the surviving disk(s). Thus, full data protection is provided by this RAID level since it always maintains a redundant copy of all data.

The down side is that only one half of the array’s raw capacity is available for use since the other half always holds a full copy of the data. This RAID level is sometimes referred to as ‘disk mirroring’.

RAID Level 5

Data stored to the disk array is first divided into equal parts and stored onto each of the array’s disks. The data segment stored to any one disk is replicated, compressed, and stored onto another disk in the array. Thus, if any one disk fails, a compressed copy of its data is always available on the surviving disks.

This allows this RAID level to offer full data protection. It can also provide reasonable performance since data transfers are typically made
in parallel to all of the disks at the same time. Since redundant data is compressed before being stored on the other disks in the array, this RAID level offers more useable capacity than RAID level 1.

The equivalent capacity of one disk is consumed for overhead with this RAID level. For example, in a 4 drive array, the total useable capacity will be equivalent to 3 of its disks.

RAID Level 10

This RAID level combines the benefits of RAID levels 0 and 1, providing both high speed and data protection. However, as with RAID 1, full duplicate copies of the data are maintained on the array (for its protection). Correspondingly, only half of the total raw capacity of the array is available for use. Keep this in mind when selecting a system’s capacity.


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