SUMMARY: what is unit_id for MSA1000 for?

Thank you to the folks that responded to my question.  The unit_id is
indeed the identifying name that the OS sees and prints it up when you use
the hwmgr or diskconfig commands.  This is optional.

---Original Question---
This is related to some of the problems I've been having with my MSA1000
and I posted for.  I've noticed on my MSA1000 that I don't have a unit_id.
This may have been lost during the firmware flashing (v4.32), or it was
never configured.  Either way, when I type "show unit_id 1", I don't have
an identifier:

CLI> show unit_id 1
No identifier created for this unit!

What is it for, if is it necessary to have one?  If I do, what should it be
set to?  I do have dual redundant MSA1000 controllers.