I will try to go into more detail later, but once any NIC card and switch or router auto-negotiate to a certain speed, the speed will be set at either 1Gbps or 100Mbps or 10Mbps. It doesn't matter what the traffic is. You can force the NIC or port to run at a certain speed. It's just best practice to use auto-negotiation. The main thing is just to insurance that any computer which is running slowly is running at the 1Gbps speed you think it is.

For nomenclature sake: you promote a server to a domain controller or demote it. You join clients to the domain or unjoin them.

Being on a domain should not affect its speed.

There are reasons to unjoin a client from a domain and joining it back. There are just times that this is the only way to fix an unfixable problem. It is also the only way to change the computer name, hence the FQDN. Fully qualified domanin name. So if the name of the computer is "main" then the FQDN will me "main.domainname.local" or "main.domainname.com"

It is good practice to have a uniform and organized way of naming computers, taking into consideration that you will have to unjoin and rejoin and, therefore, want to give it a new name. For instance the "main" computer would be better off called "office" but may be even better off called OFFICE-a. If you have to take it off the domain and rejoin, you can name it OFFICE-b. It is generally best to use a new name for active directory purposes. It will also let you know how many times that computer had to be taken off the domain.

But, the name (you can use the description for some of this, but it doesn't affect its relation to the domain) should make sense to anyone who sees it in the network list. For me, as a user, I would be very confused to see "server name" and "main computer" in the same list. Also, for purposes here, I think you would wish to refer to it as the client computer I use in my office, "OFFICE-a" or "OWNER-a" or whatever designation.

Being on a domain gives the domain controller (server) the ability to use group policy to control virus protection, updates, single sign-on and, of course a myriad of security issues. It's good to know that when a disgruntled employee walks out the door, you can disable or delete his/her account in seconds. ALWAYS BEST TO DISABLE AND NOT DELETE. Or to restore a password. Or to change a password.

Likely, the singles best reason for a domain is authentication of users. The users log in and the server authenticates their username and password, and they now have access to whatever resources that user has. With a workgroup, they are logging into a specific computer.

Using a domain or not should not affect your speeds. Taking your office computer off the domain will not slow it down or speed it up.

The single most important thing to keep in mind when you create a domain is to always make a local admin that will not be used, but that YOU as the administrator will always know. This is a local admin account for the particular computer. So, whether it is when you first install Windows to a computer or adding an account, you would want to have one local admin account that you will use for that computer and a thousand other computers. You probably will not have a thousand other controllers, but IT people do. Because anytime you take disjoin a client from a domain, you must know at least one local admin account's username and password. If not, you are fumbling around with some boot CDs that allow you to create a new one.

In your instance, I would advise making sure each computer (not the server) has a local admin account with a username such as "localadmin" and a password such as "KOBYLOCALPASSWORD". It doesn't need to be very secure. Just something you can use over and over. (I use all caps as no one else would and I only use it for this purpose). Because it will ask for the local username and password.

As far as being nervous about taking it off the domain, no need to be. It takes minutes, if that, and will let you, hopefully, get rid of the "main" name, if that is the name of the computer.

Bert
Pediatrics
Brewer, Maine