RAID Storage Explained

The most common RAID storage levels explained

RAID 0 (striping) has no redundancy. It provides improved performance and additional storage but no fault tolerance. Hence simple stripe sets are normally referred to as RAID 0. Any drive failure destroys the array, and the likelihood of failure increases with more drives in the array. A single drive failure destroys the entire array because when data is written to a RAID 0 volume, the data is broken into fragments called blocks. The number of blocks is dictated by the stripe size, which is a configuration parameter in the RAID storage controller. RAID 0 does not implement error checking, so any error is uncorrectable. More drives in the array means higher bandwidth, but greater risk of data loss.

RAID 1 (mirroring) data is written identically to multiple drives, thereby producing a "mirrored set" and at least 2 drives are required to constitute a mirror. The array continues to operate as long as at least one drive is functioning. With RAID 1 there can be increased read performance, and only a minimal write performance reduction.

RAID 5 (striping with distributed parity) RAID level 5 distributes parity along with the data and requires all drives but one to be present to operate, the array is not destroyed by a single drive failure. Upon drive failure any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. However, a single drive failure results in reduced performance of the entire array until the failed drive has been replaced and the associated data rebuilt.

RAID 6 (striping with double distributed parity) RAID level 6 provides fault tolerance of two drive failures, the array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high availability systems. This becomes increasingly important as large capacity drives lengthen the time needed to recover from the failure of a single drive. Single parity RAID levels are as vulnerable to data loss as a RAID 0 array until the failed drive is replaced and its data rebuilt, the larger the drive, the longer the rebuild takes. Double parity gives additional time to rebuild the array without the data being at risk if a single additional drive fails before the rebuild is complete.

When spanning RAID levels, a RAID type that provides redundancy is typically combined with RAID 0 to boost performance.

Some examples of this are RAID 10, RAID 50 and RAID 60

RAID 10 combines the straight block level striping of RAID 0 with the mirroring of RAID 1, making RAID 10 a stripe of mirrors and it requires at least 4 drives. RAID level 10 provides high performance and redundancy as data is simultaneously mirrored.

RAID 50 combines the straight block level striping of RAID 0 with the distributed parity of RAID 5. This is a RAID 0 array striped across RAID 5 elements and it requires at least 6 drives. RAID 50 is implemented across two or more RAID 5 arrays with data striped across the disk arrays.

RAID 60 combines the straight block level striping of RAID 0 with the distributed double parity of RAID 6. This is a RAID 0 array striped across RAID 6 elements and it requires at least 8 disks. RAID 60 is implemented across two or more RAID 6 arrays with data striped across the disk arrays.

RAID controller redundancy

RAID 5+1 or RAID 6+1 can offer RAID controller redundancy it is an array that consists of two RAID 5 or RAID 6 arrays that are mirrors of each other. Generally this configuration is used so that each RAID 5 or RAID 6 array resides on a separate controller. RAID 5+1 or RAID 6+1 can sustain the failure of all disks in either of the arrays plus up to one additional disk (RAID 5) or two additional disks (RAID 6) from the other array before suffering data loss.

Broadberry Data Systems are a market leader in Enterprise RAID Storage Solutions with a complete range of iSCSI SAN, NAS, DAS, Fibre Channel SAN and Custom RAID Storage Server Solutions.

RAID storage is an important part of our business and Broadberry Data Systems continues to improve upon its success. With Several important factors determining the correct RAID storage solution strategy for your business or organization Broadberry Data Systems can provide the best possible solution whether it is one of our NAS, iSCSI SAN, Fibre Channel SAN, Direct Attached Storage solutions or one of our custom configured RAID storage server solutions..