[Info-vax] HZS70 Unit number question

[Richard B. Gilbert]

Jeffrey H. Coffield wrote:
> I have two Alphas (not clustered) connected to a HSZ70 that currently
> has units D0 through D5 showing as DKC0 through DKC5. DKC0 through DCK4
> are mounted on one system and DKC5 is mounted on the other.
> 
> I have added some disks and want to add some new units but am concerned
> about the SCSI disk numbering and the unit numbering. AFAIK the SCSI
> controller takes a unit number (usually 7) so you could only have DKA0
> through DKA6 on a bus.

How many devices you can have on a bus depends on whether you are using 
narrow or wide SCSI.  Narrow SCSI supports a three bit device address: 
zero through seven.  Seven is usually used by the controller.

Wide SCSI gives you zero through fifteen IIRC.  ISTR that the convention 
remains that device 7 is the SCSI controller so your disks would be 0-6 
and 8-15 or something like that.

> 
> I have read the CLI reference manual on the HSZ70 and can't see any
> mention of there being a conflict between the unit number and the SCSI
> addressing. It does say that a controller can present up to 8 units on
> each target ID number. Both controllers show a SCSI target(s) of (0).
>

Never could afford an HSZ70. . . .  HSZ40 and HSZ50, yes.

> I only want to add two more units which would be DKC6 and DKC7 although
> what the actual disk unit is is not important.
> 
> 
> Jeff Coffield
> 
>