XenServer 7.2 will fail with the following error when attempting to reclaim freed space on a SSD 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
Time: 00:00:02","servernamegoeshere.com","Dec 20, 2017 9:23 AM"
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 SSDs. Others with this issue: https://discussions.citrix.com/topic/380830-reclaim-free-space-broken-in-70/?page=2#comment-1993738