Assignment of device names to external USB drives

[Denis Fortin]

Greetings,

I am trying to set up a backup server, using a combination of internal 
and external (USB) disk drives.

How can I manage the mapping of USB disk drives to device names?  i.e. 
USB drives get assigned device names like da0, da1, da2... when they are 
detected.  But if one of the drives fails or is not powered up, all 
other ones will get bumped down one in the list next time I reboot.

The problem is that if I automatically "mount /dev/da0a 
/archive/volume1", "mount /dev/da1a /archive/volume2", etc. I run the 
risk of having the wrong disk being mounted on a mount point !?!

Is there an obvious solution that I'm missing, or a canonical workaround 
to this problem?

Thanks

Denis F.