We are seeing slow performance when paging and exporting data in the webgrid.  The paging mode is set to virtual load and the virtual load mode is set to large data.  We are binding on the InitializeDataSource event and have set the DataCacheStorage to session.  With 7644 rows its taking 7 to 10 seconds to sort, filter or page.  Exporting takes 5 minutes and 17 seconds.  With 30k rows it's much much slower.  What is taking so long.  I don't understand why getting a second page of 100 rows would take significantly longer with 30k rows than it would with 1k.  Can someone explain to me why this is happening and what I can do to improve performance.