Windows NT Server includes several levels of RAID support. RAID is a technology used instead of the old SLED (Single Large Expensive Disk) design in which a hard disk failure spelled disaster. Instead of using one enormous disk drive and writing all data to that disk, RAID uses an array of less expensive and one of several methods for writing data to ensure redundancy.
Each level of RAID is designed for a specific purpose :
(i) RAID 0 - RAID 0 provides no fault tolerance because the loss of a hard disk means a complete loss of data. For this reason, some classifications omit this level of RAID.
(ii) RAID 1 - Two hard disks of equal capacity duplicate or mirror each other's contents. One disk continually and automatically backs up the other disk. This is also known as disk mirroring or disk duplexing.
(iii) RAID 2 - In this option A parity bit is just extra information that is written at the end of a file used for error checking. Checksum is an error detection scheme where each transmitted message is accompained by numerical value based on the number so set bits in the file to make sure the message isn't garbled.
(iv) RAID 3 - It requires only single redundant disk which is used as parity bit. Parity bit may be used for reconstruction of data in case a disk fails. As the data strips are small, level 3 may achieve a very high data transfer rate. However only one request can be processed at a time so there is low input/output request fulfilment rate.
(v) RAID 4 - It uses independent access technique where each of the physical disks may be accessed independently. Data strip is large and bit by bit parity strip is created for bits of strips of each disk.
In level 4 parity strip is stored on a separate disk.
(vi) RAID 5 - RAID 5 allows overlapping writes and a disk is only accessed when necessary. This level of RAD is faster and may be more reliable than some of the other methods.
Each level of RAID is designed for a specific purpose :
(i) RAID 0 - RAID 0 provides no fault tolerance because the loss of a hard disk means a complete loss of data. For this reason, some classifications omit this level of RAID.
(ii) RAID 1 - Two hard disks of equal capacity duplicate or mirror each other's contents. One disk continually and automatically backs up the other disk. This is also known as disk mirroring or disk duplexing.
(iii) RAID 2 - In this option A parity bit is just extra information that is written at the end of a file used for error checking. Checksum is an error detection scheme where each transmitted message is accompained by numerical value based on the number so set bits in the file to make sure the message isn't garbled.
(iv) RAID 3 - It requires only single redundant disk which is used as parity bit. Parity bit may be used for reconstruction of data in case a disk fails. As the data strips are small, level 3 may achieve a very high data transfer rate. However only one request can be processed at a time so there is low input/output request fulfilment rate.
(v) RAID 4 - It uses independent access technique where each of the physical disks may be accessed independently. Data strip is large and bit by bit parity strip is created for bits of strips of each disk.
In level 4 parity strip is stored on a separate disk.
(vi) RAID 5 - RAID 5 allows overlapping writes and a disk is only accessed when necessary. This level of RAD is faster and may be more reliable than some of the other methods.
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