MicroNet Genesis V User's Guide download pdf (Page 14)

Introduction

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Dual-level RAID achieves a balance between the increased data availability

inherent in RAID 1 and RAID 5 and the increased read performance inherent in

disk striping (RAID 0). These arrays are sometimes referred to as

RAID 0+1 or

RAID 10 and RAID 0+5 or RAID 50.

In summary:

! RAID 0 is the fastest and most efficient array type but offers no fault-

tolerance. RAID 0 requires a minimum of two drives.

! RAID 1 is the best choice for performance-critical, fault-tolerant

environments. RAID 1 is the only choice for fault-tolerance if no more than

two drives are used.

! RAID 3 can be used to speed up data transfer and provide fault-tolerance

in single-user environments that access long sequential records. However,

RAID 3 does not allow overlapping of multiple I/O operations and requires

synchronized-spindle drives to avoid performance degradation with short

records. RAID 5 with a small stripe size offers similar performance.

! RAID 5 combines efficient, fault-tolerant data storage with good performance

characteristics. However, write performance and performance during drive

failure is slower than with RAID 1. Rebuild operations also require more

time than with RAID 1 because parity information is also reconstructed. At

least three drives are required for RAID 5 arrays.

! RAID 6 is essentially an extension of RAID level 5 which allows for addi-

tional fault tolerance by using a second independent distributed parity

scheme (two-dimensional parity). Data is striped on a block level across

a set of drives, just like in RAID 5, and a second set of parity is calcu-

lated and written across all the drives; RAID 6 provides for an extremely

high data fault tolerance and can sustain multiple simultaneous drive

failures. Perfect solution for mission critical applications.

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MicroNet Genesis V User's Guide Page 14