I powered off one VM with two 2Tb disks, overall coalesce time was about 3-4 hours.
Running VM still has VDI to coalesce. I found proccess "/usr/bin/vhd-util coalesce --debug -n /dev/VG_XenStorage-de024eb7-ce14-5487-e229-7ca321b103a2/VHD-b5d6ab41-50dc-4116-a23c-e453b93ce161"
Can I run it again to parallel coalesce process?