Usable storage of PS6210XS

Hello everyone,

I am in the middle of looking at a storage hardware refresh, and I am currently looking at the PS6210XS with 17x1.2TB 10K SAS and 7x800GB SSD drives, which has a raw capacity of 26TB.  I am aware that this array can only have RAID6 accelerated configured, so I am therefore wondering if someone could let me know the actual "usable" capacity after RAID and hotspares have been taken into consideration?

Many thanks.