SQL services use 100% Harddisk when queries

Question

I developed  my own app to query the data from MSSQL
I use MSSQL 2008 R2
when I run the query in MSSMS, it's work fine and has very fast response
but when I run with C# application (integrated query inside).
it take about 5000ms for 1 query and when I exterminate the task manager, I found that the services of my database engine using disk load about 5-7 MB/s (but the % is 100%)  
after some experiment. I found out that if I want to make the query faster in my C# app, I have to open the MSSMS "together" (and make any select top 1000) with my query in C# app
anyone know what is MSSMS do to increase the performance of any running services?
**Note that it happens only some PC not all of them. 

Answer 1

>but when I run with C# application (integrated query inside).
It is better to write server side stored procedures and call them from client C# apps.
BOL: "Benefits of Using Stored Procedures
The following list describes some benefits of using procedures.
Reduced server/client network traffic          
The commands in a procedure are executed as a single batch of code. This can significantly reduce network traffic between the server and client because only the call to execute the procedure is sent across the network. Without the code encapsulation provided
by a procedure, every individual line of code would have to cross the network.
Stronger security          
Multiple users and client programs can perform operations on underlying database objects through a procedure, even if the users and programs do not have direct permissions on those underlying objects. The procedure controls what processes and activities
are performed and protects the underlying database objects. This eliminates the requirement to grant permissions at the individual object level and simplifies the security layers.
The EXECUTE AS
clause can be specified in the CREATE PROCEDURE statement to enable impersonating another user, or enable users or applications to perform certain database activities without needing direct permissions on the underlying objects and commands. For example,
some actions such as TRUNCATE TABLE, do not have grantable permissions. To execute TRUNCATE TABLE, the user must have ALTER permissions on the specified table. Granting a user ALTER permissions on a table may not be ideal because the user will effectively
have permissions well beyond the ability to truncate a table. By incorporating the TRUNCATE TABLE statement in a module and specifying that module execute as a user who has permissions to modify the table, you can extend the permissions to truncate the table
to the user that you grant EXECUTE permissions on the module.
When calling a procedure over the network, only the call to execute the procedure is visible. Therefore, malicious users cannot see table and database object names, embed Transact-SQL statements of their own, or search for critical data.
Using procedure parameters helps guard against SQL injection attacks. Since parameter input is treated as a literal value and not as executable code, it is more difficult for an attacker to insert a command into the Transact-SQL statement(s) inside
the procedure and compromise security.
Procedures can be encrypted, helping to obfuscate the source code. For more information, see SQL Server Encryption.
Reuse of code          
The code for any repetitious database operation is the perfect candidate for encapsulation in procedures. This eliminates needless rewrites of the same code, decreases code inconsistency, and allows the code to be accessed and executed by any user or application
possessing the necessary permissions.
Easier maintenance          
When client applications call procedures and keep database operations in the data tier, only the procedures must be updated for any changes in the underlying database. The application tier remains separate and does not have to know how about any changes
to database layouts, relationships, or processes.
Improved performance          
By default, a procedure compiles the first time it is executed and creates an execution plan that is reused for subsequent executions. Since the query processor does not have to create a new plan, it typically takes less time to process the procedure.
If there has been significant change to the tables or data referenced by the procedure, the precompiled plan may actually cause the procedure to perform slower. In this case, recompiling the procedure and forcing a new execution plan can improve performance.
LINK: http://technet.microsoft.com/en-us/library/ms190782.aspx
Optimization:
http://www.sqlusa.com/articles/query-optimization/
Kalman Toth Database & OLAP Architect
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