 
             (cb) =>
                 num_chunks = Math.ceil(size / chunk_size)
+                # do not use Sha1 -- even though that might be nice in theory and for some sort of (highly unlikely!) dedup,
+                # in practice it would require reference counting and making the code much more complicated and error prone.
                 chunk_ids = (uuid.v4() for i in [0...num_chunks])
 
                 dbg("saving the chunks")

        streams : required  # path to streams
        limit   : 1
        verbose : false
        cb      : undefined

    dbg = (m) -> winston.debug("storage_migrate: #{m}")

                        if err
                            dbg("syncing #{project_id} resulted in error: #{err}")
                            errors[project_id] = err
                        setTimeout(c, opts.timeout*1000)  # let it break
            async.mapLimit(files, opts.limit, f, cb)
    ], (err) ->
        if err
