SAS and SATA encapsulation

                                                         EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
                  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                    E
                  +                                      E                                +                    E
********************          *******************        E  *******************     BBBBBB+BBBBBBBBBBBBBBBBBB  E
*                  *          *                 *+++++++++++*                 *     B     +                 B  E
*  SAS controller  *++++++++++*  SAS Expander   *++++++  E  *  SAS Expander   *     B     +                 B  E
*                  *          *                 *     +  E  *                 *++++++++*******************  B  E
********************          *******************     +  E  *******************     B  *                 *  B  E
                  |                          |        +  E           |              B  *     SAS HDDs    *  B  E
                  |                          |        +++++++++++++++++++++++++++++++++*                 *  B  E
                  |                          |           E           |              B  *******************  B  E
                  |                          |           E           |              B                       B  E
                  |                          |           E           |              B                       B  E
                  |                          |           E           |              B  *******************  B  E
                  |                          |           E           ------------------*                 *  B  E
                  |                          ------------------------------------------*    SATA HDDs    *  B  E
                  ---------------------------------------------------------------------*                 *  B  E
                                                         E                          B  *******************  B  E
                                                         E                          BBBBBBBBBBBBBBBBBBBBBBBBB  E
                                                         EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
Legend:

+     SAS  physical Link, optionally carrying ATA commands encapsulated in the SCSI logical layer.
-     SATA physical Link - same limitations as all "normal" SATA links (up to 1m cable)
B     Backplane - Electrically transparent (at least from the drives' perspective), does no conversions
E     Enclosure - The box that takes the drives, optionally includes an SAS Expander