Depending on usage, Sakai may create many large temporary files in the system temporary file storage location (e.g. /tmp). It is a good practice to routinely remove temporary files older than a day, especially if you have a lot of users or have heavy usage of mail sending with attachments. Note that you should not simply remove all temp files on a schedule as some of them may be in active use (also be careful about removing temp files which are used by other processes).