Slice Evacuations is cleanup process initiated as part of an operation that releases a slice to return slices to a pool. The message occurs because the internal pool filesystem does not have enough free space (note this is not the overall lun or pool). Evacuation requires the filesystem to have sufficient free space to hold the data being moved off the slices being evacuated. The free space is from provisioned slices instead of from the pool. If at any point during the evacuation CBFS determines there is insufficient free space in the pool filesystem, to complete the evacuation it will report the failure of the evacuation process by invoking the evacuation callback with a unique status code (0x7, CBFS_NoSpace.) So even though there may be adequate free slices in a pool, it can also run into CBFS_NoSpace state during evacuation, however this is working as intended and should not cause alarm.