This might be intentional change but causes lots of issues with maintaining historical data on most Cisco modular devices (Nexus 7k/Catalyst 6500). In 1.12.0 it appears that the data collection directory structure changes the existing directory from a simple description to adding MAC addresses to the directory name. This causes a big issue because when the name of the directory changes this creates new jrb files and all historical data collection is lost. In addition to that scenario, if you swap line cards or supervisor engines the interface/system MAC address can change and again the directory name changes again where the historical data is lost. This is easy enough to simply move the old jrb files into the new directory but when there are 1000's that is a bigger issue. Others on the list have also reported issues regarding this behavior on other types of systems as well.
Example after upgrade from 1.10.9 to 1.12.0:
drwxrwxrwx 2 root root 4096 Aug 19 08:47 Vlan99
drwxrwxr-x 2 root root 4096 Aug 19 08:58 Vlan99-0026981a16c1