Proware SB-1413-UA, Руководство по установке и настройке

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USB and eSATA to SATA II RAID Subsystem
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Installation and Configuration Manual
RAID 3 sector-stripes data across groups of drives, but one drive in the group is dedicated to storing
parity information. RAID 3 relies on the embedded ECC in each sector for error detection. In the case
of drive failure, data recovery is accomplished by calculating the exclusive OR (XOR) of the information
recorded on the remaining drives. Records typically span all drives, which optimizes the disk transfer
rate. Because each I/O request accesses every drive in the array, RAID 3 arrays can satisfy only one
I/O request at a time. RAID 3 delivers the best performance for single-user, single-tasking
environments with long records. Synchronized-spindle drives are required for RAID 3 arrays in order to
avoid performance degradation with short records. RAID 5 arrays with small stripes can yield similar
performance to RAID 3 arrays.
Under RAID 5 parity information is distributed across all the drives. Since there is no dedicated parity
drive, all drives contain data and read operations can be overlapped on every drive in the array. Write
operations will typically access one data drive and one parity drive. However, because different records
store their parity on different drives, write operations can usually be overlapped.
Dual-level RAID achieves a balance between the increased data availability inherent in RAID 1 and
the increased read performance inherent in disk striping (RAID 0). These arrays are sometimes referred
to as RAID 0+1 or 1+0.