Questions about load balancing by Dovecot Director

Issue

We were testing Dovecot Director with 2 Dovecot backends, and 10 user accounts.

As a result of testing, 10 user accounts were distributed to 2 backends as 3:7. The destination backend appears to be dependent on the user account. Please answer the following questions.

• Q1) How is the distribution of users to the backend determined?
• Q2) Can Dovecot Director distribute user accounts as evenly as possible to backends? If yes, how?
• Q3) Is it possible to configure Dovecot Director to fix a specific user or domain to one of the backends, with failover to the other backend if the first one fails, and recover back to the fixed backend once it is available again?