title: Should I increase the size of my MongoDB oplog file?
body: <p>I understand that the oplog file will split multi updates into individual updates but what about batch inserts? Are those also split into individual inserts? </p>
  
  <p>If I have a write intensive collection with batches of ~20K docs being inserted roughly every 30 seconds, do I / should I consider increasing my oplog size beyond the default? I have a 3 member replica set and mongod is running on a 64 bit Ubuntu server install with the Mongodb data sitting on a 100GB volume.</p>
  
  <p>Here is some data which may or may not be helpful:</p>
  
  <pre><code>    gs_rset:PRIMARY&gt; db.getReplicationInfo()
      {
          "logSizeMB" : 4591.3134765625,
          "usedMB" : 3434.63,
          "timeDiff" : 68064,
          "timeDiffHours" : 18.91,
          "tFirst" : "Wed Oct 24 2012 22:35:10 GMT+0000 (UTC)",
          "tLast" : "Thu Oct 25 2012 17:29:34 GMT+0000 (UTC)",
          "now" : "Fri Oct 26 2012 19:42:19 GMT+0000 (UTC)"
      }
      gs_rset:PRIMARY&gt; rs.status()
      {
          "set" : "gs_rset",
          "date" : ISODate("2012-10-26T19:44:00Z"),
          "myState" : 1,
          "members" : [
              {
                  "_id" : 0,
                  "name" : "xxxx:27017",
                  "health" : 1,
                  "state" : 1,
                  "stateStr" : "PRIMARY",
                  "uptime" : 77531,
                  "optime" : Timestamp(1351186174000, 1470),
                  "optimeDate" : ISODate("2012-10-25T17:29:34Z"),
                  "self" : true
              },
              {
                  "_id" : 1,
                  "name" : "xxxx:27017",
                  "health" : 1,
                  "state" : 2,
                  "stateStr" : "SECONDARY",
                  "uptime" : 76112,
                  "optime" : Timestamp(1351186174000, 1470),
                  "optimeDate" : ISODate("2012-10-25T17:29:34Z"),
                  "lastHeartbeat" : ISODate("2012-10-26T19:44:00Z"),
                  "pingMs" : 1
              },
              {
                  "_id" : 2,
                  "name" : "xxxx:27017",
                  "health" : 1,
                  "state" : 2,
                  "stateStr" : "SECONDARY",
                  "uptime" : 61301,
                  "optime" : Timestamp(1351186174000, 1470),
                  "optimeDate" : ISODate("2012-10-25T17:29:34Z"),
                  "lastHeartbeat" : ISODate("2012-10-26T19:43:59Z"),
                  "pingMs" : 1
              }
          ],
          "ok" : 1
      }
  
  gs_rset:PRIMARY&gt; db.printCollectionStats()
  dev_fbinsights
  {
      "ns" : "dev_stats.dev_fbinsights",
      "count" : 6556181,
      "size" : 3117699832,
      "avgObjSize" : 475.53596095043747,
      "storageSize" : 3918532608,
      "numExtents" : 22,
      "nindexes" : 2,
      "lastExtentSize" : 1021419520,
      "paddingFactor" : 1,
      "systemFlags" : 0,
      "userFlags" : 0,
      "totalIndexSize" : 1150346848,
      "indexSizes" : {
          "_id_" : 212723168,
          "fbfanpage_id_1_date_1_data.id_1" : 937623680
      },
      "ok" : 1
  }
  </code></pre>