Online conversion of a running container from VZFS to Ploop format might fail with the output like this:
[root@hwnode ~]# vzctl convert 100 --velayout 5 Tracker started rsync : file has vanished: "/vz/tmp/vzmigrate.LeF2Eo/var/spool/postfix/incoming/1126E281E003" rsync : file has vanished: "/vz/tmp/vzmigrate.LeF2Eo/var/spool/postfix/maildrop/ED1B42832001" rsync : rsync warning: some files vanished before they could be transferred (code 24) at main.c(1039) [sender=3.0.6] rsync exited with code 24 Invalid parameter vzpp vzpp-plesk vzpp-desktop Umounting CT#100 ... /usr/sbin/vzctl exited with code 32 Can't move/copy CT#100 -> CT#100, ,  : /usr/sbin/vzctl exited with code 32
Due to high activity in the container, files can be created and deleted while the conversion operation is in progress.
rsync reports exactly this error after it has copied all data.
If it is possible then perform offline conversion to avoid such issues.
~# vzctl stop 100 ~# vzctl convert 100 --velayout 5
To repeat the conversion, it is necessary to clean up from the previous attempt: delete the directory with the created Ploop image.
~# rm -rf /vz/private/100/root.hdd ~# vzctl convert 100 --velayout 5