If you are using a slow HDD you can optimise Kontakt to use more RAM by changing the DFD buffer size.
When an instrument is using the Direct-from-disk (DFD) streaming, Kontakt will load a tiny portion of each sample into memory. This pre-load buffer gives Kontakt a little bit of data in RAM that it can play while it's streaming in data from the disk. Kontakt allows you to configure how big this buffer is on an instrument or global level so that users can optimise for SSDs or other fast data storage.
If you have a fast solid-state drive, you can often get away with setting the buffer as low as 6KB with no problems or streaming issues. However, with a slow HDD you will likely need to increase this. By default the value is set to 60KB, however it is recommended to try increasing this further if you are still having issues.
Globally changing the DFD Buffer Size
1) With Kontakt open, choose Settings.
2) Select Memory
3) Adjust the buffer size accordingly. This will change for all instruments that you load.
Changing the DFD Buffer Size by Instrument
1) Open the Spitfire Instrument that you wish to edit.
2) Open the Instrument Settings
3) Adjust the buffer size accordingly. This will only apply to the instrument selected, provided that you do not have a global override set.