Table 6.2 Typical Hard Disk Drive Parameters Characteristics Seagate Barracuda ES.2 Seagate Barracuda 7200.10 Seagate Barracuda 7200.9 Seagate Hitachi Microdrive Application High-capacity server High-performance desktop Entry-level desktop Laptop Handheld devices Capacity 1 TB 750 GB 160 GB 120 GB 8 GB Minimum track-to-track seek time 0.8 ms 0.3 ms 1.0 ms — 1.0 ms Average seek time 8.5 ms 3.6 ms 9.5 ms 12.5 ms 12 ms Spindle speed 7200 rpm 7200 rpm 7200 5400 rpm 3600 rpm Average rotational delay 4.16 ms 4.16 ms 4.17 ms 5.6 ms 8.33 ms Maximum transfer rate 3 GB/s 300 MB/s 300 MB/s 150 MB/s 10 MB/s Bytes per sector 512 512 512 512 512 Tracks per cylinder (number of platter surfaces) 8 8 2 8 2Table 6.3 RAID Levels Category Level Description Disks Required Data Availability Large I/O Data Transfer Capacity Small I/O Request Rate Striping 0 Nonredundant N Lower than single disk Very high Very high for both read and write Mirroring 1 Mirrored 2N Higher than RAID 2, 3, 4, or 5; lower than RAID 6 Higher than single disk for read; similar to single disk for write Up to twice that of a single disk for read; similar to single disk for write 2 Redundant via Hamming code N + m Much higher than single disk; comparable to RAID 3, 4, or 5 Highest of all listed alternatives Approximately twice that of a single disk Parallel access 3 Bit-interleaved parity N + 1 Much higher than single disk; comparable to RAID 2, 4, or 5 Highest of all listed alternatives Approximately twice that of a single disk 4 Block-interleaved parity N + 1 Much higher than single disk; comparable to RAID 2, 3, or 5 Similar to RAID 0 for read; significantly lower than single disk for write Similar to RAID 0 for read; significantly lower than single disk for write 5 Block-interleaved distributed parity N + 1 Much higher than single disk; comparable to RAID 2, 3, or 4 Similar to RAID 0 for read; lower than single disk for write Similar to RAID 0 for read; generally lower than single disk for write Independent access 6 Block-interleaved dual distributed parity N + 2 Highest of all listed alternatives Similar to RAID 0 for read; lower than RAID 5 for write Similar to RAID 0 for read; significantly lower than RAID 5 for write N = number of data disks; m proportional to log
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