I setup ocs so that the disk info is shown from main page, so to generate a report including that info I just have to do an export from ocs reports all computers main page.
I managed to do so adding several custom fields for disk info (free size, capacity, fs type, fs name) and extract and copy the disk info from storages table into the accountinfo custom fields added every hour from crontab, by using sql sentences.
I do things like that to include all the info that I need to be included in reports.