rsync --delete

[Dexter <dexter@madalbal.sk>]

Hi,
i use "rsync -rlptgov --delete /mnt/server/dir/ /var/share/server/dir"
comand to sinchronize directory on backup server with primary server. I
use --delete option, so that files, that do not exist on SRC are deleted
also on DST. SRC directory is mounted through NFS on backup server.
Acording to manual, rsync should not delete any files if there are any
I/O errors, to prevent masive deletion. But masive (whole tree) deletion
happened to me, when SRC directory was not mounted and directory
"/mnt/server/dir/" was empty.
Do you know some way to evoid this to happen?
Thanks alot.
     Dexter