SHARKOON 5-Bay RAID-Station - Manual (Page 35)

5-bay raid station 35
11.8 R5 mode
Function:
The R5 mode requires a minimum of three drives to implement. The R5 mode adds fault
tolerance to drive striping by including parity information with the data. R5 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. There are
at least three members to a virtual R5 volume. The following example illustrates how the
parity is rotated from drive to drive.
Advantage/disadvantage:
The R5 mode uses less capacity for protection and is the preferred method to reduce the
cost per megabyte for larger installations.
In exchange for low overhead necessary to implement protection, the R5 mode degrades
performance for all write operations. The parity calculations for R5 mode may result in
write performance that is somewhat slower than the write performance of a single drive.
The resulting storage capacity of the virtual R5 volume will be four times of the smallest
drive.
If one drive fails, the virtual R5 volume is still usable, but it is in a vulnerable state
because its mirrored hard drive is inaccessible. When the offline drive comes back online,
the appliance begins a rebuild process immediately to restore data redundancy. During
this procedure the LED indications will notify you that a rebuild is in progress.
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