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Disk Duplexing, sometimes mistakenly referred to as “Disk Mirroring” is a means of duplicating and saving data to provide data protection. It consists of copying data onto two hard disks, each on a separate disk channel, simultaneously.
Disk Duplexing was developed as a method to protects data in the event of a hard disk failure, or in the event of a hard disk channel failure between a given disk and the server. The hard disk channel includes the disk controller and interface cable. If any component on one channel fails, the other disk on a separate channel can continue to operate without data loss or interruption of work routines because it is on a different channel.
Should a failure occur, the operating system sends a warning message to the user console that a drive or component has failed, giving the user the opportunity to restore the duplexing protection as soon after a failure as possible without interrupting work flow.
WARNING: Because the warning message can scroll off the console screen before you see it, we recommend that you check the status of disk mirroring periodically to ensure that the channels are synchronized.
NOTE: Duplexing by itself does not guarantee data protection. If both disk channels were to fail at the same time, or should the computer itself fail, the potential for lost data still exists. Back up your data regularly!
Disk duplexing allows the same data to be written to all disks simultaneously. Since the disks are on different channels, data transfer is faster than with disk mirroring, where data is written to the disks sequentially over the same channel.
Disk duplexing also allows split seeks. This sends read requests to whichever disk can respond first. Multiple read requests are also split between the duplexed disks for simultaneous processing.
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