http://pyatilistnik.org/gruppyi-dostupnosti-alwayson/
http://www.sql.ru/blogs/dbasimple/2011
https://docs.microsoft.com/ru-ru/sql/database-engine/database-mirroring/set-up-login-accounts-database-mirroring-always-on-availability?view=sql-server-2017
https://support.microsoft.com/ru-ru/help/918992/how-to-transfer-logins-and-passwords-between-instances-of-sql-server
http://dbasimple.blogspot.com/2013/05/ms-sql-server.html
ReadOnly
http://www.sqlservercentral.com/articles/always+on/167193/
