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The mirror server.
The mirror server in the cluster is the solution of dual system hardware configuration of the most simple and low prices of most, usually mirroring service hardware configuration requires two servers, with independent operating system disk and hard disk data stored on each server, each server and client is connected with the network card, a card or completion of mirror mirror function card.
The mirror server has simple configuration, convenient use, low price and many other advantages, but due to the mirror server needs to use the image data network, to achieve data synchronization by mirroring software, so you need CPU and memory resources occupied by the web server, the mirror server performance is lower than the performance of a single server.
Some of the mirror server cluster system uses the memory image technology, the advantage of this technique is that all applications and network operating system in two servers mirror synchronization, when a host fails, the backup machine can take over almost without feeling the situation with applications. Because the two server memory completely consistent, but when the system application with defects resulting in system downtime, two servers will synchronize downtime. Implementation of data synchronization is the memory card or a card, in the course of reading and writing two servers will not synchronous data in some states in the large amount of data, so the mirror server for users who are not high, budget less on cluster system requirements.
Hardware configuration example:
The network server two server operating system disk two
The server data storage disk users need to determine
Server mirroring card ( part of the software can use the standard card ) two
Network service card two block three, dual and disk array
Compared with the mirror server dual system, dual and disk array cabinet interconnection structure of a disk array cabinet, third party production at present, many companies omnivision, precision industry company, production of disk array cabinet, disk array controller card is installed in the disk array cabinet, array cabinet can directly in the hard disk cabinet a logical disk array configuration. Disk array cabinet is connected via a SCSI cable with server SCSI card, system administrators need to directly to disk in a disk array cabinet configuration.
Memory mirroring technology does not adopt dual and disk array cabinet interconnection structure, therefore need to have a certain switching time ( usually 60? D? D180 seconds ), it can be effective to avoid the defects of the application itself lead to system downtime, and because all the data are stored in the disk array cabinet built-in, when work machine fails, the backup machine to replace the work machine, reading data from a disk array, so it will not generate data without synchronization problem, because this scheme does not require a network mirror synchronization, so the performance of the server cluster scheme is much higher than the mirror server structure.
Dual and disk array cabinet interconnection structure has the disadvantage of single point fault defects in the system, the so-called single point fault refers to when a system or an application failure, cause all down all systems. In this system the disk array cabinet will lead to single point fault, when the disk array cabinet logical or physical failure, all data will be lost, therefore, in the selection of the scheme, choose a better quality and after sale service product.
Hardware configuration example:
The network server two
The server operating system disk two
Third party production of disk array cabinet a
Disk cabinet for SCSI wire.
Disk array cabinet data storage hard disk as the user needs to determine
Network service card two
In addition, some manufacturers have more excellent technical solutions, such as HP.
