The server may not have enough memory or the operating system is swapping.
The import performance depends not only on the servers CPU, but primarily on the server I/O subsystem. Thus we recommend to run FSI Server on a dedicated machine.
If FSI Server tries to import images that can’t be handled in memory it will use it’s own disk based methods to handle the data. The less memory there is available the earlier FSI Server needs to fall back to using these disk based methods which are of course slower. So if you are importing large images more memory might speed up the import process.
Before falling back to disk based image handling, FSI Server will use direct memory. This is mapped to RAM by the operating system.