Why is my volume capacity is lower than expected?

There are several things that factor into the usable capacity of your ReadyNAS volume.

Disk manufacturers use 1GB = 1000^3, whereas most modern operating systems, including RAIDiator, use 1GB = 1024^3. This means a 500GB disk will show up as 465 GB in FrontView.
RAID requires one disk capacity to maintain redundancy. This means if you have 4 x 500GB disks, your end usable capacity will be 3 x 500GB.
RAIDiator operating system takes up roughly 2.25GB per disk.
The overhead of RAID and filesystem takes up roughly 2% of the total space.
Snapshot space takes up 5GB by default during installation. This is resizable.

For example, let's calculate the usable capacity of a 4 x 500GB system in RAID 5 or X-RAID mode. For simplicity, we'll calculate this based on

Raw capacity (GB = 1000^3) = 2000 Conversion to (GB = 1024^3) = 1862 Minus one disk for redundancy (-465) = 1397 Minus OS (10) = 1387 Minus RAID/Filesystem overhead (2%) = 1359 Minus snapshot reserved space (5GB) = 1354

Based on our calculation, the approximate usable capacity for a 4 x 500GB system is 1354GB.

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