SQL CE 

SQL Compact Edition or CE is the default database used when utilizing the standard installation, which is the simplest SkySync installation possible. SQL CE and the standard installation are best used for smaller customers as there are some inherent limitations. SQL CE can only have up to 3 million folder and file objects and is limited to a 4GB database size. Additionally it is more difficult to move a SQL CE database to a new server, where as SQL express and Full SQL are much more portable. Additionally the use of SQL CE will also limit SkySync to running no more then 2 jobs simultaneously. 

SQL Express and Full SQL

SQL Express and Full SQL allow for 6 jobs to run simultaneously and is required for larger installations. The major difference between the 2 is that SQL Express has a maximum database size of 10GB where as full SQL had a max size of 524PB (petabyte). Additionally Full SQL is capable of using multiple computers to create its database. In order to use SQL or SQL Express is must be first installed and setup on the server containing it. Additionally a "SkySync" database will need to be created and it is advised that a user specific to SkySync be created with ownership rights to the Database as well. The user, database name, and user password will all be required during the install.