From a technical standpoint, Luwak has some problems with the way in which files are chunked and manifest of those chunks is maintained.
Specifically, there is no good way of knowing when a given chunk is no longer in use, which creates a very thorny distributed garbage collection issue -- this is a fundamental design problem. In addition, the manifest of chunks does not properly handle situations where siblings of the manifest occur -- this is a significant implementation problem. These two issues, in particular, have led us to stop further development of Luwak and investigate other architectural approaches.
Above and beyond these technical issues, Luwak also doesn't solve a host of other problems that most people who want to store files in Riak encounter. We are in the process of building a complete solution for multi-tenancy file storage in Riak -- more info on that will be available next month.
中还没有看到对Large Object Support的支持。