Refer http://httpd.apache.org/docs/2.2/vhosts/fd-limits.html
When using a large number of Virtual Hosts, Apache may run out of available file descriptors (sometimes called file handles) if each Virtual Host specifies different log files. The total number of file descriptors used by Apache is one for each distinct error log file, one for every other log file directive, plus 10-20 for internal use. Unix operating systems limit the number of file descriptors that may be used by a process; the limit is typically 64, and may usually be increased up to a large hard-limit.
Does Virtualmin handle this issue? Do we have an option in Virtualmin to specify a common log file and split it before the stats are generated?