title: Slow read performance on Mongo under Centos 6
body: <p>I successfully basic configure my replica set, but i noticed slow read performance. I have 2 mongo servers and 1 arbiter in my replica set. All are running on Centos 6.3 minimal setup (just database).</p>
  
  <p>I also have single mongo instance on another  Windows server 2012.</p>
  
  <p>Before i build my replica set, my web server was on same OS as Mongo (that windows instance). Performance was fine, results was like</p>
  
  <p>C# .NET 4.5 (IIS and Mongo on same VM) Read 2000 rows : ~250ms at AvgObj 2600 bytes</p>
  
  <p>Now with my replica set i have very slow read performance. When my web server access replica set, i`m getting result like</p>
  
  <p>C# .NET 4.5 (separated, IIS and Mongo on Centos Replica) Read 2000 rows : ~2500ms at AvgObj 2600 bytes</p>
  
  <p>I tried to read from my single Mongo instant from remote IIS and result is like</p>
  
  <p>C# .NET 4.5 (separated, IIS and Single Mongo on Windows) Read 2000 rows : ~600ms at AvgObj 2600 bytes</p>
  
  <p>All servers are running in single physical machine with Hyper-V core server.</p>
  
  <p>Im using latest C# MongoDB Driver 1.7 version. From what i tested in command shell, on all mongo servers my query is executed in 10ms.</p>
  
  <p>Can anyone give me suggestions why my replica set on separated Centos servers have slow read performance? is it network, drivers or what else?</p>
  
  <p>My C# config is </p>
  
  <pre><code>            var server1 = new MongoServerAddress("1.0.0.1"); //primary
              var server2 = new MongoServerAddress("1.0.0.2"); /secundary
              var servers = new List&lt;MongoServerAddress&gt; {server1, server2};
  
              var safe = new MongoClientSettings
                  {
  
                      Servers = servers,
                      ReplicaSetName = "rs0",
                      ConnectionMode = ConnectionMode.ReplicaSet,
                      WriteConcern = new WriteConcern
                          {
                              Journal = false,
                              W = 1
                          },
                      ReadPreference = new ReadPreference
                          {
                              ReadPreferenceMode = ReadPreferenceMode.PrimaryPreferred
                          }
                  };
  </code></pre>