That php issue should be solved for awhile now, also deploy proper php.ini settings for each domain.
ea:
[PATH=s:/webroot/domain.nl]
open_basedir = s:/webroot/domain.nl
doc_root = s:/webroot/domain.nl
error_reporting = E_ALL & ~E_NOTICE
error_log = s:/logging/php/domain.nl.errors.log
upload_tmp_dir = s:/webroot/domain.nl/uploads
session.save_path = s:/webroot/domain.nl/sessions
upload_max_filesize = 32M
post_max_size = 8M
disable_functions = "curl_exec,curl_multi_exec,dl,exec,parse_ini_file,passthru,popen,proc_open,proc_close,shell_exec,show_source,symlink,system"

That if: use map and an if.

As for storage, here we use a Debian VM as storage concentrator, nginx talks to Debian on IP level and Debian manages/caches all kinds of storage units as one pool.
(mapping a drive is slow, use direct ip access)

You might also benefit from speed when using separated lan connections.

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nginx for Windows http://nginx-win.ecsds.eu/