Production

    - Ensure we detect and replay a failed txn involving blobs forward or
      backward at startup.

Far future

      More options for blob directory structures (e.g. dirstorages
      bushy/chunky/lawn/flat).

      Make the ClientStorage support minimizing the blob cache. (Idea: LRU
      principle via mstat access time and a size-based threshold) currently).

      Make blobs able to efficiently consume existing files from the filesystem

Savepoint support
=================

 - A savepoint represents the whole state of the data at a certain point in
   time

 - Need special storage for blob savepointing (in the spirit of tmpstorage) 

 - What belongs to the state of the data?

   - Data contained in files at that point in time

   - File handles are complex because they might be referred to from various
     places. We would have to introduce an abstraction layer to allow
     switching them around... 

     Simpler solution: :
