Putting the journal on a different storage device and channel (not a different partition on the same device) is useful. Separating the index and the data, even on different storage devices and channels, provides almost no utility. The only reason to separate data/index/journal files to separate devices (on separate channels) is to permit overlapped physical I/O. Logical separation is not particularly useful. Bitty-boxes typically do no have I/O facilities which have separate communication channels to independent devices so there is no benefit to be achieved by any separation of journal, data, or index.