Turning a nonclustered into a clustered where the attachments are in the file system doesn't automatically migrate the attachments to the db when the cluster is started, nothing shows up in attachmentdata. If you try to migrate manually afterwards you get

java.lang.IllegalArgumentException: Source and destination attachment dao must not be the same instance for migration

despite attachment storage showing as filesystem. Also all the images show up as broken links in the wiki after the attempted migration. The files are still in the original attachment folder.