Exactly.

In fact, its Total & Target Server Memory are far below its Physical Memory, and high in Paging File(Total) % Usage : around 28 %, high PhysicalDisk (Total) % Disk Time and high PhysicalDisk (Total) Avg. Disk Queue Length.

I think it might be due to : low memory usage, thus, the server will use page file very frequently, so, it got a high Paging File % and high Physical Disk % Disk time and disk queue length.

So, I want to know how to increase its Target and Total Memory usage.