PLANET NAS-7400 User Manual
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The RAID Volume’s data capacity equals the capacity of the smallest disk
drive times the number of disk drives. For example, one 100 GB and three
120 GB drives will form a 400 GB (4 x 100 GB) RAID Volume instead of 460
GB.
If disk drives of different capacities are used, there will also be unused
capacity on the larger drives.
Because RAID 0 does not offer Fault Tolerance, meaning that you cannot
recover your data after a disk drive failure, RAID 0 Volumes on NAS-7400
consist of one or more disk drives.
7.1.2 RAID 1 – Mirror
When a RAID Volume is mirrored, identical data is written to a pair of disk
drives, while reads are performed in parallel. The reads are performed using
elevator seek and load balancing techniques where the workload is
distributed in the most efficient manner. Whichever drive is not busy and is
positioned closer to the data will be accessed first.
With RAID 1, if one disk drive fails or has errors, the other mirrored disk
drive continues to function. This is called Fault Tolerance. Moreover, if a
spare disk drive is present, the spare drive will be used as the replacement
drive and data will begin to be mirrored to it from the remaining good drive.
Data Mirror
disk drives
RAID 1 Mirrors identical data to two drives
The RAID Volume’s data capacity equals the smaller disk drive. For example,
a 100 GB disk drive and a 120 GB disk drive have a combined capacity of 100
GB in a mirrored RAID Volume.
If disk drives of different capacities are used, there will also be unused
capacity on the larger drive.
RAID 1 Volumes on NAS-7400 consist of two disk drives.