How does XWiki behave when disk space is low?

XWiki can behave very oddly when disk space is low and XWiki running on Apache Tomcat and/or using MySQL or other database system cannot write log or temporary or to other files on disk. Observed behaviour includes: Tomcat and MySQL crashing, etc. To the user XWiki appears to 'lose' attachments, velocity scripts display errors on wiki pages, etc. So it is easy to think these 'errors' are due to some other underlying problem when it is simply a question of lack of disk space.

On unix/linux type installations (where tomcat and mysql host their data directories on /var and /var is low on disk space or even full) you can stop xwiki, tomcat, and mysql, etc and move those data directories to a bigger partitition and use symbolic links to reference the new locations.

So the moral of the story is to keep an eye on disk space and make sure you don't run out of disk space!