  Fibre Channel Device Naming? 
 The Question is:
 
I am connecting 2 different storage arrays to one OVMS AlphaServer through an
 FC switch.  The CU and LDEV numbers are used to create a 'DG' device name at
 the OS level.  I have an application that uses similarly configured arrays
 (same CU and LDEV numbers
) in each array.
 
My problem is that when I have multipath running (MPDEV_ENABLE), the DG device
 name resolves as having 2 different paths to the device.  It is true that 2
 different paths exist to the same device name, but, in this case, they are not
 the same device, they
 are on different arrays that may not have the same data on them.
 
When I disable multipath, only 1 DG device shows up.  It is not clear to me
 which device that is, as the complete path with WWN is not shown at the SHOW
 DEVICE/FULL prompt.
 
Can I tailor OVMS to recognize these 2 devices as being different, even they
 have the same CU and LDEV number?
 
 The Answer is:
 
  The OpenVMS Fibre Channel device drivers and the associated code
  supplied with OpenVMS will not produce the symptoms described,
  when used with a correctly-functiong and correctly-configured HSG
  series storage controller.
 
  Details of the hardware and software and firmware involved here will
  be required.  Please contact the Compaq Customer Support Center.
 
  OpenVMS depends on the user-selected unit identification value set
  in the Fibre Channel Storage Controller to assign the device name,
  and all Fibre Channel devices present and configured are all assumed
  to be named $1$DGA[identifier]:
 
  At the Storage Controller:
 
    HSG&gt; set unit d17 identifier=1234
 
  To enable the visibility of the device to the Alpha SRM console:
 
    P00&gt;&gt;&gt; set mode diag
    P00&gt;&gt;&gt; wwidmgr -quickset -udid 1234
    P00&gt;&gt;&gt; init
    ...
    P00&gt;&gt;&gt; show device
 
  The identifier is returned via a SCSI command in the vendor-specific
  command set unique to the HSG series storage controllers.
 
  There is an allocation class setting in various Fibre Channel
  controllers, but OpenVMS does not use this value -- OpenVMS assigns
  all Fibre Channel disk devices into allocation class one.
 
  The OpenVMS Alpha Fibre Channel disk configuration process is
  separate from the Alpha SRM console console wwigmgr setting.
  Details on Fibre Channel configuration and operation are available
  in the Fibre Channel documentation at the OpenVMS website.  (A direct
  URL to this portion of the website is listed in the OpenVMS FAQ.)
 
