                             else
                                 dbg("blob is expired, so nothing to be done, ever.")
                                 cb()
-                async.mapLimit(v, 3, f, cb)
+                async.mapLimit(v, 2, f, cb)
             (cb) =>
                 dbg("successfully wrote all blobs to files; now make tarball")
                 misc_node.execute_code


    _disconnect_if_idle: =>
        if new Date() - @_last_activity > 1000*@_idle_timeout_s
            @close()

    _reconnect: (cb) =>
        misc.retry_until_success

        opts = defaults opts,
            limit : 10000     # number of blobs to backup
            path  : required  # path where [timestamp].tar file is placed
            repeat_until_done : 0 # if positive keeps re-call'ing this function until no more results to backup (pauses this many seconds between)
            cb    : undefined # cb(err, '[timestamp].tar')
        dbg     = @dbg("backup_blobs_to_tarball(limit=#{opts.limit},path='#{opts.path}')")
        join    = require('path').join
