Howard Miller

It depends what you did. Moodle never deletes the config file. So, if you drop the database and start again it will use any config file it finds. It skips the config file creation step.

This is usually a good thing. Copying config-dist.php and editing config.php myself is my preferred way of doing things.

But, yeh, character set and collation problems can be a pain.

My first thought is - have you run out of disk space for your database?

That "Temporary file write failure" is NOT a good thing. Something is stopping MySQL writing files.

Running

OPTIMIZE TABLE mdl_logstore_standard_log;

*should* sort this out.

I don't believe there is a limit.

However, I doubt the UI is designed with hundreds of groups in mind. I also don't know if this would ever have been extensively tested. So, while it should be ok if you run with very large numbers of groups you may find difficulties.

I'm not sure I see the problem. Surely whoever controls the DNS for ClientDomain.com just points the hostname LMS.ClientDomain.com to your server? Job done.