Usman Asar

@Albert, I can +1 on IIS's performance as had to remotely change a school's moodle from Apache to IIS because they were having performance issues, same hardware resources allocated on VM, after switch I was forwarded the messages of students telling "incredible speed difference", and that backup issues would be resolved since PHP 7 on 64-bit.

@Constance : I as well upgraded moodle version to latest 3.0.3 first thing right after switch from Apache to IIS - Absolutely no issues there. if you're having trouble setting up Moodle on IIS, get me moodle, moodledata and MySQL backup and i'll do whole setup for you without costing a penny.

There would have been issues in the past, since PHP support on Windows platform was limited to 32-bit with limited support for 64-bit, so large courses restore and backups could have been, since PHP 7 it comes with full support for 64-bit in windows platform. One catch though, So far only Moodle version 3.0.1 (onwards) are tested and certified to use with PHP 7, so i'll recommend upgrading your Moodle, or meanwhile use older versions of PHP 5.x.x until you upgrade.

Assuming your guys are good enough in setting up IIS environment for Moodle, if not, there is full tutorial on setting up IIS on Windows Server 2012 R2 for Moodle HERE. another recommendation, making use of Zend OpCache (that moodle recommends as well) together with WinCache plug-in specifically built by IIS team to accelerate PHP applications., and they have recently updated it for PHP 7 as well.

If you dont have hardware already, I'll as well recommend going through whole post.

OK no worries, when you mentioned you've set time out of 4 hours, was it PHP you've set into or Apache?

There are 3 ways you can set time outs

1: Using .htaccess file

ini_set( 'session.gc_maxlifetime' , 14400);

2: Using Apache's config file

TimeOut 14400

3: Using php.ini file

session.gc_maxlifetime = 14400;

you can also set in php.ini

session.cache_expire = 15000;

and

session.cookie_lifetime = 0 (0 donates cookie staying alive until browser windows closes)

Russell, which server it is? I meant O/S and WebServer?

Doan, is it load balancing IP's or load balancing servers?

blank page usually points towards corrupted caches, so assuming your user cache for admin account has corrupted, delete "cache" and "localcache" folders from your moodledata folder and refresh page and see if you can log-in, dont worry about deletion of two folders, for they will automatically be re-created once you refresh webpage.