The Aperture library tracks every project, album, folder, original, and version, no matter whether the photos, video files, and audio files are stored in the Aperture Library file or in other hard disk locations. Aperture automatically creates a library file in the Pictures folder the first time you open Aperture. You can import media into the library or have Aperture access the files in other locations. When you back up your originals to vaults on external hard disks, those actions are tracked by the Aperture library as well. For more information about backing up your library, see Plan your backup system
In Aperture you can:
Work with multiple libraries: You can work with as many libraries as necessary—including iPhoto libraries—and switch between them without having to quit and reopen Aperture. If your workflow calls for several unique libraries, you can switch between them on the fly. You can also check the contents of a library prior to importing it into the library that’s currently open. For more information, see Create new libraries and View other libraries.
Merge libraries: You can also transfer libraries from other systems running Aperture and merge them with the library on your local Aperture system. All links between versions and their original photos are maintained when projects are transferred. This is particularly useful if you use a portable computer when on location or away from your studio, and a workstation at your studio. For more information, see Merge libraries.
Move a library to another location: When the library file becomes large and requires more disk space than is available in its current location, you can move it to a hard disk with greater storage capacity. To change the location of the library, you move the library file to a new location and then double-click it to open it in Aperture. You specify where the library is located using the Preferences window. For information about working with multiple library files in Aperture, see General preferences and View other libraries.
Tip: To maximize performance, place the library file on an internal hard disk.