1. A method of storing data, the method comprising: storing a first version of a document in a first structure on a storage device; receiving an updated version of the document; identifying one or more frequently updated portions of the document; storing on the storage device the one or more frequently updated portions of the document, in a second structure separate from the first structure; receiving a request for the document; retrieving the first version of the document from the first structure and the frequently updated portions of the document from the second structure; merging the updated portions with the first version to obtain a merged version of the document, by writing the updated portions to the first version of the document; and returning the merged version of the document in response to the request.
1. A method of storing data, the method comprising: storing a first version of a document in a first structure on a storage device; receiving an updated version of the document; identifying one or more frequently updated portions of the document; storing on the storage device the one or more frequently updated portions of the document, in a second structure separate from the first structure; receiving a request for the document; retrieving the first version of the document from the first structure and the frequently updated portions of the document from the second structure; merging the updated portions with the first version to obtain a merged version of the document, by writing the updated portions to the first version of the document; and returning the merged version of the document in response to the request. 4. The method of claim 1 , wherein said identifying comprises: observing updates to the document over a period of time; and during said observing, recognizing at least one portion of the document as being accessed more frequently than other portions of the document; wherein the one or more frequently updated portions of the document include the at least one portion.