1. A system, comprising: one or more processors; one or more computer-readable media storing one or more computer programs for execution by the one or more processors, the one or more computer programs comprising instructions for: using a plurality of chunks to implement a hierarchical file system comprising a plurality of volumes in a content-addressable storage system; wherein each volume of the plurality of volumes is an encrypted volume or a non-encrypted volume; storing a plurality of unencrypted chunks in the content-addressable storage system corresponding to the non-encrypted volumes; storing a plurality of encrypted chunks in the content-addressable storage system corresponding to the encrypted volumes; providing an application for execution on a client computer, wherein the application is configured to perform: obtaining volume state information for a particular volume, the volume state information comprising a chunk key for a root chunk of a hierarchy of chunks corresponding to the particular volume; retrieving particular data stored in the content-addressable storage system for the particular volume by performing: when the particular volume is not encrypted, retrieving one or more unencrypted chunks from the content-addressable storage system corresponding to the particular data; when the particular volume is encrypted, retrieving one or more encrypted chunks from the content-addressable storage system corresponding to the particular data, and decrypting the one or more encrypted chunks, wherein, when the particular volume is not encrypted, retrieving the particular data is performed by a folders and files layer of the application that make calls directly to a chunk system layer that retrieves one or more unencrypted chunks from the content-addressable storage system, wherein, when the particular volume is encrypted, retrieving the particular data is performed by a volume encryption layer of the application that make calls directly to a chunk system layer that retrieves one or more unencrypted chunks from the content-addressable storage system.