CentOS 5 :: Unable To Make Full Backup?

I'm trying to add a scheduled full backup to the crontab file, but the full backup never completes; it always stops somewhre in the file system. I guess is b/c the os is updating those files or has them open. I've tried to use the --exclude options but still it always hangs somewhere else.... this is what I'm usingtar -zcvpf /mnt/storage/backup/fullbackup1.tar.gz --exclude=/mnt --exclude=/sys --exclude=/proc --exclude=/lost+found --exclude=/net --exclude=/srv / > /mnt/storage/backup/fullbackup.log