By default, all Drupal Cloud sites come with a [istdraft:hostname].mit.edu URL. However, IS&T has worked with CSAIL to also provide sites that use the csail.mit.edu subdomain.
If you want a CSAIL hostname for your site, include it in the name you choose in the Create Site form. For example, if you only enter "mysite" in the form, your Drupal Cloud site URL will be mysite.mit.edu, but if you enter 'mysite.csail' in the form, your site URL will be mysite.csail.mit.edu.
Please note that there is a maximum length of 22 characters, including the '.csail' portion. This means thisisalongname.csail is valid, while thisisaloongname.csail is not.
By default, the form will fill in the Site Owner field with the email address associated with the kerberos ID of the person filling in the form. If you are requesting a site on behalf of another user and wish them to be the owner with administrative rights, be sure to enter the email associated with their kerberos ID, so that they may log in using Touchstone and their MIT certificate.
TIG has posted more information for CSAIL members on their wiki.