# Backup
The main aim of Principia DJ Musica is to provide an archive of digital music that persists for many years, therefore it is critical to have a backup process in place. The backup process should be automatic and follow the 3-2-1 backup rule. That is:
* 3 copies of the data are maintained
* 2 copies are stored on different media
* 1 backup copy is kept off-site
One way to achieve this is to have a full copy of the archive and library on a laptop, a full copy of the archive and library on a NAS device on the local network and full copy of the archive and library backed up to a cloud storage provider. It must be setup so that changes to files on either the laptop or the NAS device are automatically sync’d to the other (a 2-way sync). The archive and library on the NAS device is then continuously backed up to a cloud storage provider via the internet.
My system consists of a laptop and a NAS device on my local network that is always on. I use Resilio Sync (https://www.resilio.com/individuals/?utm_source=navbar&utm_medium=synchome) to automatically do a 2 way sync between the laptop and NAS. Resilio Sync is awesome software and is available for number of different operating systems and as plugins for a number different NAS devices including Synology, QNap and Drobo. I then have Crashplan (https://www.crashplan.com/en-us/) running on my NAS device which continuously backs-up to the Crashplan cloud storage servers.
As a bonus feature I can use my desktop computer to access my music archive and library on the NAS share and do cpu intensive things such as key & bpm detection and format transcoding much faster than on my laptop. These changes are then automatically sync’d back to my laptop by Resilio Sync the next time it is connected to my local network.
