Datto drive instances are tied together by a term we call your subdomain. The subdomain is the portion of the URL that comes before .dattodrive.com.
You can quickly check if your desired subdomain is available by attempting to navigate to the subdomain.dattodrive.com. In my example I attempted to navigate to abctest.dattodrive.com which came back with a 404 error. This indicates that the subdomain is available because it is currently not hosting an instance.
Another way to check is by attempting to sign up on our website https://dattodrive.com/. In the event the subdomain is taken you will not be able to grant it and instead it will send an email to the subdomain owner if you want to request access to it.
This is helpful because sometimes other employee's of your organization may of already made a datto drive instance for your organization.