Hitachi has reclaim zero pages on enterprise level storage (VSP)
This is mostly used in combination with software on the machine.
For instance, with ASM, you can reclaim zero pages from ASM, then reclaim on storage.
A nice document :
https://www.hds.com/assets/pdf/recla...on-utility.pdf
There is an article on RHEL network regarding :
https://access.redhat.com/solutions/45514
It involves creating a lvol with all free space from volume group, dd-ing the lvol with using /dev/zero, removing the lvol, remount with discard and running fstrim.
After that you can reclaim the storage space from storage GUI/command line.
Dunno how would you apply the same on raw volume tho (no VG).
Hope that helps.
Regards
Peasant.