RAID1- - 5 technologies details is solved (in)
From;    Author:Stand originally

Although RAID 0 can provide more spaces and better performance, but whole system is very fluky, if appear breakdown, cannot undertake any remedying. So, RAID 0 just is in those is opposite commonly the ability below the case with data security not high demand is used by people.

RAID 1 and RAID 0 are disparate, on the dependability that its skill stress puts in what how can affecting the utmost below the circumstance of function to assure a system entirely and reparability. RAID 1 is a cost of the implementation in all RAID grade is highest kind, nevertheless, people or choice RAID 1 will save those decisive important data.

RAID 1 is called again disk mirror, the mirror that each disk has a correspondence dish. Write to the data of any disk can be duplicated mirror dish in; The system is OK from a group of mirrors dish medium any disk reads access to occupy. Apparent, disk mirror can raise systematic cost for certain. The space that can use because of us is the half of summation of all disk capacity only. Issueing what the graph shows is the disk mirror that comprises by 4 hard disk, can be two hard disk only as what storage space uses among them (those who draw oblique line for mirror part) .

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Below RAID 1, what the breakdown of an any hard disk won't affect a system is normal move, and want to be able to assure a pair of any mirrors only dish in at least a disk can be used, RAID 1 can count the hard disk of the quantity to appear in the half even the uninterrupted job when the problem. When invalidation of a hard disk, the system is met oversight this hard disk, turn and use the rest mirror dish read keep data.

Normally, we weigh the RAID system of breakdown of occurrence hard disk to demote to be in move below mode. Although be saved at this moment data still can continue to use, but RAID system will no longer reliable. If the rest mirror dish also appear problem, so whole system can break down. Accordingly, we ought to change in time the hard disk of attaint, avoid to appear new issue.

Change new dish later, original good dish of medium data must be duplicated new dish in. This operates mirror of the synchronism that be called. Synchronous mirror needs for a long time commonly, it is such more when the size of the hard disk that should damage especially is very large. In synchronous mirror in having a process, the outside won't be affected to the visit of data, but because duplicate data needs to take up the bandwidth of one part, may make the function of whole system drops somewhat so.

Because RAID 1 basically is,show disk mirror realistically through be being read 2 times, the load of disk controller is quite so big also, write often into the environment of data in need especially. To avoid occurrence function bottleneck, use many disk controller to appear very be necessary. Signal laying a plan the disk mirror that uses two controller.
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