sccache defaults to using local disk storage. You can set the SCCACHE_DIR environment variable to change the disk cache location. By default it will use a sensible location for the current platform: ~/.cache/sccache on Linux, %LOCALAPPDATA%\Mozilla\sccache on Windows, and ~/Library/Caches/Mozilla.sccache on MacOS.
The default cache size is 10 gigabytes. To change this, set SCCACHE_CACHE_SIZE, for example SCCACHE_CACHE_SIZE="1G".
The local storage only supports a single sccache server at a time. Multiple concurrent servers will race and cause spurious build failures.