E-Series Controller Firmware
When trying to reclaim deleted blocks or space from E-Series thin provisioned volume, space is not reclaimed and the host SCSI UNMAP operation returns with an error.
SCSI UNMAP was first introduced in E-Series controller firmware starting 8.25.05, which means deleted blocks will not be reclaimed on a volume that was created prior to this release. Once the controller firmware level support this feature, SCSI UNMAP should be enabled on each thin-provisioned volume created prior to 8.25.05. See the following links to enable this feature according to the host OS:
FA24: What are Windows host operating system considerations when using SCSI UNMAP with E-Series thin volumes?
FA25: What are VMware considerations when using SCSI UNMAP with E-Series thin volumes?
FA26: What are Linux host operating system considerations when using SCSI UNMAP with E-Series thin volumes?
Some platforms cannot be upgraded beyond 8.20 and therefore SCSI UNMAP is not supported on these platforms. From customer product communication CPC-1705-03:
"SANtricity OS 8.20 is at the end of engineering support as of May 1, 2017. The E2600, E5400, and EF540 systems cannot be upgraded beyond SANtricity OS 8.20."