PPS supports persistent storage across reboots. This storage requires a reliable filesystem.
If you need to persist an object to specialized hardware such as a small NVRAM (which doesn't support a filesystem), you can create your own client that subscribes to the PPS object to be saved. On each object change, PPS will notify your client, allowing the client to update the NVRAM in real time.
The persistence directory where PPS objects are stored uses exactly the same directory hierarchy as the PPS root directory. Object persistence is, therefore, limited by the path and filename lengths as well as the directory nesting limits of the underlying filesystem.
For example, the QNX Neutrino NFS server supports a maximum nesting depth of 15 levels. This limit also applies to PPS using this service.