Any other caching than var/cache? / Flush Magento Cache works, rm -rf var/cache not

Question

We did an update on production but still a translation which was newly defined in a translate.csv file did not work.

After rm -rf var/cache it still was not shown. We verified that the folder is empty. /tmp/magento also did not exist. After refreshing the page var/cache got filled again - so it is in fact used.

We were able to make it work by Flush Magento Cache in the backend - how can this be? Where else might the translation be cached?

edit

We found this in the local.xml

    <cache>
    <backend>apc</backend>
    <prefix>APC_</prefix>
    </cache>

The question is why Magento still writes to the cache folder.