Not a mandriva user but others can confrim this but I think this is whre mandriva stores downlaoded rpm updates. Also you say they are files, I they are directories. Synaptic/Apt does the same to store downloaded rpms but uses /var/cache/apt.
If /var/log/messages and others is that large after 2 days then see whats in them. dmesg command will show most of that. Just to make sure you are seeing it correctly use the command ' ls -lha ' in /var/logs directory. The h makes the it more humanly readable. Default is bytes.