Contemporary disc systems of RAID
the concept of redundant arrays of low-cost drives, Redundant Arrays of
Inexpensive Disks (RAID), and describe the basic configuration of RAID (levels).
There are three main trait RAID- arrays: set physical disks from a user's
perspective is a single virtual disk large capacity; - distributed data on
recruitment drives; in recruiting there Abundant capacity, providing an
opportunity to recover data when there is a failure of one or more disks. RAID
Level determined by way of distribution and use of redundant tanks way. Of the
five RAID- levels, as described in the article, levels of 1.3 and 5 encountered
considerable interest in the industry. In addition, two more have been proposed
RAID- level: 0 and 6. Consider the features RAID levels. Let conditionally
consider that RAID- array is a set of physical disks only connected to the
computer, and does not contain any additional logic than the minimum necessary
to ensure data exchange.
RAID-0.
RAID-0 is not redundant capacity. The failure of any drive leads to the
impossibility of access to the data and can lead to a loss. (Formally, it should
not be used for this configuration symbol RAID-0. perhaps correct to refer to it
as RAID-0). The distribution of data is carried out on physical disks to read.
The cumulative memory space is divided into segments of equal length. Designate
these segments of the letters A, B, C, etc. Segment A physically located on the
first drive, V-segment on the second disc in the same location as the first A, C-segment
in the third, and the segment 0-for the fourth. The fifth segment is placed
again on the first drive after the segment A, sixth in the second segment,
followed by B, and so on until all seggmenty not be distributed in all physical
disks. Performance data distribution will vary depending on the ratio of size
and length of the segment-read / write file. First, the size of a large segment
relative to the size of the file. In his small portion (shaded). When recording
or reading only recourse to this part of the segment in the second drive. Most
queries such ratio to the size of the file size segment will relate to a single
segment. When reading data virtual address into a physical address is displayed
segment on the disk containing the data. The data read from the segment. Similar
actions implemented and with the record. Since then almost every request would
be consistent with the only segment, multiple disks in the array will be able to
serve different requests in parallel. This ensures good performance of requests
for small and medium sized.
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