Sans Digital MobileRAID MR8UT6G, Руководство пользователя

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The R50 mode adds fault tolerance to drive striping by including parity information with
the data. R50 mode dedicates the equivalent of one drive for storing parity stripes. The
data and parity information is arranged on the drive array so that parity is written to all
drives (SYS1 and 2). The following example illustrates how the parity is rotated from
drive to drive.
The R50 mode uses less capacity for protection compare to RAID 1 / mirroring and is
the preferred method to reduce the cost per megabyte for larger installations.
In exchange for low overhead necessary to implement protection, the R50 mode
degrades performance for all write operations. The parity calculations for R50 mode
may result in write performance. The resulting storage capacity of the virtual R50
volume will be “n minus 2” where (n=number of disks) of the smallest drive capacity.
If one drive fails, the virtual R50 volume is still usable, but it is in a vulnerable state
because additional drives failure will have data lost. When the defective drive is
replaced, the enclosure begins a rebuild process immediately to restore data
redundancy. During this procedure the LED indications will notify you that a rebuild is
in progress.
11.3 RAID50 mode
Function :
Advantage/disadvantage :