Adaptec 133U2 User Guide - Page 140
RAID 0/1 Arrays, RAID 5 Arrays
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Adaptec CI/O Management Software User's Guide RAID 0/1 Arrays Maximum Disks Allowed: 16 (or as allowed by your controller)(must be an even number)1 Minimum Disks Allowed: 4 RAID 0/1 disks use from two to eight pairs of disks. They are called mirrored arrays because both disks in each pair contain the same data. The read and write performance of a RAID 0/1 array is much better than that of a single physical disk. RAID 0/1 arrays are highly reliable; the array data remains safe so long as at least one disk of each mirrored pair is good. Thus, in a 12-disk RAID 0/1 array, the array could continue working with up to six failed disks if one disk in each pair is still good. Because of the mirrored arrangement, RAID 0/1 arrays require twice as many disks as the actual amount of storage space. RAID 5 Arrays Maximum Disks Allowed: 162 (or as allowed by your controller) Minimum Disks Allowed: 3 RAID 5 arrays contain redundant information in the form of parity data, which is calculated block-by-block for all user data. The parity data is distributed across all the disks in the array and occupies the equivalent capacity of about one disk. User data is interspersed with this parity data. If one disk in the array fails, its data can be reconstructed from the user data and parity data on the other disks. Two disks must fail before the entire array fails. The read performance of RAID 5 arrays is excellent and is comparable to that of a RAID 0 array. Write performance is slower than that of a RAID 0 array, because new parity data must also be calculated and written when user data is written. Ì 1 The maximum would be 14 disks if the system has a single SCSI channel. 2 The maximum would be 15 disks if the system has a single SCSI channel. 10-16
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