Sakai currently does not inform the user when file uploads fail due to lack of space. This has been fixed for Resources (SAK-2353), but is still an issue with other tools.
The original report against resources indicates:
If you upload a file to Resources and the destination space is full, you'll still see the file listed in Resources as though the transfer succeeded. When you try to access the file, however, it'll turn out to be 0 bytes in size.
WARN org.sakaiproject.component.legacy.content.DbContentService$DbStorage@1f0c45f failed to write resource /user/marith/Weasel/Another 800kb doc.rtf java.io.FileNotFoundException /afs/ir/class/saki/content1/2005/236/19/d8a323a3-066c-478a-80f5-33aa73b4c659 (No space left on device) (2005-08-24 122829,356 TP-Processor3_org.sakaiproject.component.framework.log.CommonsLogger)
Aug 24, 2005 122840 PM org.apache.catalina.startup.HostConfig checkResources