Memory for disk arrays
Advantages: -- easy implementation; -- Ease array recovery in the event of
failure (copying); -- just for high speed applications with great intensity
queries; -- the speed record is identical to the speed record for one drive, and
the speed of reading the data twice as high than one drive. Disadvantages: --
low efficiency in the use of drive space; -- the high cost per unit volume - 100%
redundancy. Disk Arrays zero and the first to use appropriate levels of the
system, processing large amounts of data and the critical speed chte-niya/zapisi.
i. RAID 2 - tolerant disk array using Hamming Code ECC) RAID Level 2 - a scheme
backup data using Hamming code for corporate correction of errors. Recordable
figures are not based on the modular structure, as in RAID 0, but on the basis
of words, the amount equal to the number of words discs for recording data in
the array. Every single bit recorded on a separate disk array. For example, if
the array has four disk recording data, the sequence of four bits, that is a
word written on each of the disks is the way that the first bit is written on
the first drive, the second bit - on the second, etc. In addition, for each word
is calculated error correction code (ESS), which records being allocated to the
disks for storing control information (Figure 6). The number of bits in the
context trolnom word and the number of disks required for the storage of the
control information is calculated by the following formula: L = K log2 Q - words
digit data. Naturally, with this formula in calculating L rounded to the next
higher whole to the nearest whole number. To avoid contact with the formulas,
you can use a scrap-mnemonicheskim Human: Words digit checklist determined by
the number of bits required for the submission of binary decent size words.
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