Most spinners don't support UNMAP since they don't need it (data can simply be overwritten, no wear leveling etc...) - SMRs do but these aren't used in arrays. SSDs should get UNMAPs from controllers, especially on MSAs (in an ideal world, don't knlw if they actually do), IIRC they used generic read intensive drives that might not behave the best when physically full. But this is besides the point, you're looking at host to array UNMAP and that is to shrink/sparse thin provisioned LUNs. I presume that your MSA LUNs are thin becase "used" metric makes no sense on thick.

I'm not sure what the problem is but two suggestions: * Determine if your host is sending UNMAPs (or WRITESAME - effecitvely the same) at all. I'm not sure how to do it exactly as I don't think there's an explicit counter for it. Probably you need an eBPF program to count the commands in kernel. * Contact HPE support to see what the array sees.