There are several things that factor into the usable capacity of your ioSafe R4 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.
