Yes, your terminology usage is correct. Presenting array capacity to managers and executives can be challenging becuase they don't always understand the difference between the manufacturers drive capacity (Hitachi 146GB Drive), array vendor raw capacity (133GB), and the usable capacity once RAID and Hot Spare assignment has been calculated. For instance I tell my CIO that we are buying an enclosre of 2TB SATA drives. He thinks we just bought 30TB of storage, when in reality there will be at most 22TB of usage storage if you have one hot spare and two R5 6+1 RAID groups (the 2TB drive is 1.8TB raw). He wants to know what happened to the 8TB. So it all depends on how savvy your manager is and how you plan on configuring the array. Your RAID overhead can be anyware from 10% to 50% of raw capactiy depending  the RAID type used.
Hi,  I have limited experience with the san so please keep it simple and sorry if this is a repetitive question. Clariion CX3-40 - navisphere manager 6.26  I ran a storage report and it showed: "Unused raid group capacity (GB)" Total     disk     raid0...          raid5 1835     blank     blank          1030   "Unused physical disk capacity (GB)" Total     bus0 enc0 ...          bus3 enc 1 1073     0 ...                         1073  created a raid group and it showed 894 usable free added 500GB lun to raid group - so far so good.  once completed, I ran a storage report and it showed: "Unused raid group capacity (GB)" Total     disk     raid0...          raid5 2140     blank     blank          1335   "Unused physical disk capacity (GB)" Total     bus0 enc0 ...          bus3 enc 1 blank     0 ...                         0  how do i find the usable space in a report? and why did my extra GB disappear? and what things take away from the RAW drive capacity (vault space, raid - what else?)  Thanks.
Where did my space go?