XenServer 7.2 will fail with the following error when attempting to reclaim freed space on SAS RAID array and SATA RAID array:
"Failed","Reclaiming freed space on SR 'Local storage'
blkdiscard: /dev/VG_XenStorage-5e3bb883-fe1b-e4d0-401c-4006fe1efeb2/5e3bb883-fe1b-e4d0-401c-4006fe1efeb2_trim_lv: BLKDISCARD ioctl failed: Operation not supported
XenServer refuses to cleanup failed migration storage that I have no access to remove, thus eating up all local storage space. This was not an issue with XenServer 5.x or 6.x with SAS and SATA disks. Others with this issue: https://discussions.citrix.com/topic/380830-reclaim-free-space-broken-in-70/?page=2