If you need to display a large amount of records in a GridControl, you can use server data-binding modes (synchronous or asynchronous). These are specifically designed to work with large sets of data consisting of more than 50,000 records.
Take a look at Server Mode concepts to start with these modes.
With XtraGrid and LINQ you can start from here:
Server Mode: Binding to a Data Source Using 'LINQ to SQL Classes'
P.S. The Data Source Configuration Wizard simplifies the process of binding a data-aware DevExpress control (such as GridControl) to a data source