From the mongodb tutorial of how to resync a set, I wipe all the files in /data/db and restart the mongod process to resync the data. Everything looks ok, I get the same number of documents as the existing two sets(primary and one secondary). However, when I check the memory on MMS. it shows me my new resynced set/mongod process has a different memory status value than the other two. For existing twos using db.serverStatus.mem shows like the following:

"mem" : {
    "bits" : 64,
    "resident" : 239,
    "virtual" : 66348,
    "supported" : true,
    "mapped" : 32865,
    "mappedWithJournal" : 65730
}

however, the new resynced set shows like:

"mem" : {
    "bits" : 64,
    "resident" : 1239,
    "virtual" : 52447,
    "supported" : true,
    "mapped" : 25700,
    "mappedWithJournal" : 51400
}

the resynced resident memory is 6-10 times more than the existing ones. I wouder if it is normal because all data comes in suddenly during the resyncing?? and even virtual and mapped value are different too. Can anyone explain?? thanks