Additional sa devices?

[Marcus Reid]

  Hi,

  I just plugged in an old SCSI tape changer, and got the following
  devices:

    lrwxr-xr-x  1 root  wheel            6 Jul 10 03:28 esa0 -> esa0.0
    crw-rw----  1 root  operator    0,  96 May 14 05:43 esa0.0
    crw-rw----  1 root  operator    0, 102 May 14 05:43 esa0.1
    crw-rw----  1 root  operator    0, 105 May 14 05:43 esa0.2
    crw-rw----  1 root  operator    0, 108 May 14 05:43 esa0.3
    lrwxr-xr-x  1 root  wheel            6 Jul 10 03:28 nsa0 -> nsa0.0
    crw-rw----  1 root  operator    0,  95 May 14 05:43 nsa0.0
    crw-rw----  1 root  operator    0, 101 May 14 05:43 nsa0.1
    crw-rw----  1 root  operator    0, 104 May 14 05:43 nsa0.2
    crw-rw----  1 root  operator    0, 107 May 14 05:43 nsa0.3
    lrwxr-xr-x  1 root  wheel            5 Jul 10 03:28 sa0 -> sa0.0
    crw-rw----  1 root  operator    0,  94 Jul 10 03:45 sa0.0
    crw-rw----  1 root  operator    0, 100 May 14 05:43 sa0.1
    crw-rw----  1 root  operator    0, 103 May 14 05:43 sa0.2
    crw-rw----  1 root  operator    0, 106 May 14 05:43 sa0.3
    crw-rw----  1 root  operator    0,  93 May 14 05:43 sa0.ctl

  My question is what the difference is between 'sa0.0' and 'sa0.[1-3]'.
  I can't seem to find it documented anywhere.

  Thanks,

  Marcus