If you modify a document in such a way that it grows
the document size, there is a chance that MongoDB will have to move the
document to some other place in the physical file. There is fixed cost
involved in the move and Mongo may decide to grow the size of your data files
to accommodate the move.
To account for this, Mongo maintains a discover on how often documents in each collection grow and then pads some extra space around the document in the physical file so that the document can grow a bit and not have to be moved. This discover is called the padding factor (or paddingFactor).
If the padding factor is higher for a collection, it indicates that the documents are growing.
Update/ReIndex to take care of the performance.
To account for this, Mongo maintains a discover on how often documents in each collection grow and then pads some extra space around the document in the physical file so that the document can grow a bit and not have to be moved. This discover is called the padding factor (or paddingFactor).
If the padding factor is higher for a collection, it indicates that the documents are growing.
Update/ReIndex to take care of the performance.