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Disks Small I/O Large I/O Data Request Rate Transfer Capacity Data Availability Required Very high for both read Lower than Very high N and write single disk Up to twice that of a Higher than single disk Higher than RAID 2, single disk for read; similar to sin- for read; lower than or 5; 4, 3, 2N similar to single disk gle disk for write RAID 6 for write Much higher than single Approximately twice Highest of all listed comparable to disk; m + N that of a single

Description Nonredundant Mirrored Redundant via Ham- ming code parity Bit-interleaved Block-interleaved parity Block-interleaved distributed parity Block-interleaved dual distributed parity proportional to log N

RAID Levels Level 0 1 2 3 4 5 6 m number of data disks;

Table 6.3 Category Striping Mirroring Parallel access Independent access = N

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