Support for mixed or write-heavy workloads on non-HDFS filesystems

We can support reasonably well use cases on non-HDFS filesystems, like S3, where an external writer has loaded (and continues to load) HFiles via the bulk load mechanism, and then we serve out a read only workload at the HBase API.

Mixed workloads or write-heavy workloads won't fare as well. In fact, data loss seems certain. It will depend in the specific filesystem, but all of the S3 backed Hadoop filesystems suffer from a couple of obvious problems, notably a lack of atomic rename.

This umbrella will serve to collect some related ideas for consideration.