Ember data and mongodb state?

Question

According to http://emberjs.com/api/data/classes/DS.EmbeddedRecordsMixin.html

Records without an id property are not considered embedded records, model instances must have an id property to be used with Ember Data.

If thats so how would i use a model like:

 {
    "_id": "545b54f20dbd7015f015359a", 
    "comments": [
        {
            "msg": "what is this jelly", 
            "time": "1415271666", 
            "user": {
                "id": "53fefc9ee4b07d3fe92fc077", 
                "username": "kfir124"
            }
        }
    ], 
    "files": [
        {
            "key": "1415271653.39af9c9fb8cc8b49dcaac5eec72614ce85.jpg", 
            "order": 0
        }
    ], 
    "time": "1415271666", 
    "uploader": {
        "id": "53fefc9ee4b07d3fe92fc077", 
        "username": "kfir124"
    }
}  

So uploader may be an embedded record but what about files and comments? they are both arrays of objects which do not live outside of the main model's namespace therefore they have no IDs