As Simon Burge wrote...
> On Tue, 9 Feb 1999 00:22:40 -0800 (PST)  Ross Harvey wrote:
> 
> > > does anybody have an /etc/disktab entry for the DEC RZ56 harddisk ?
> > 
> > I wouldn't worry too much about it, just copy one of the existing entries
> > and adjust the main partition, or forget disktab and put it straight into
> > the disklabel. The scsi drives all id themselves at boot and tell you how
> > big they are. The sectors/track varies between cylinders on modern drives,
> > and this renders the tracks/cylinder parameter meaningless as well, except
> > to the extent that they should all describe a self-consistent hypothetical
> > drive. The ffs still works to layout things contiguously or at least nearby,
> > and this results in good performance even if the geometry is unknown.
> 
> Well, the comments from a friendly Ultrix box confirm this:
> 
> # NOTE: The RZ58 uses a recording technique called zoned recording.

An RZ56 != RZ58

RZ56 -> Micropolis 1588 with DEC specific firmware. I don't think it
does ZBR.

> #   Using this technique, the number of sectors per track will vary
> #   depending on what zone of the disk is in use (simply multiplying 
> #   ns*nt*nc does not give true capacity of the drive).  The ns (number
> #   of sectors per track) is calculated by "ns = total sectors/(nt*nc)"
> #   and is a rounded value.  Therefore, the value "ns" is an approximation,
> #   not a true representation, of what is stored on disk. 
> #    
> #   The 'c' partition listed below gives the true size of the RZ58
> #   (this information can be obtained by use of the DEVGETGEOM ioctl). 
> # 
> 
> rz58|RZ58|DEC RZ58 Winchester:\
> 	:ty=winchester:ns#85:nt#15:nc#2112:\
> 	:pa#32768:ba#8192:fa#1024:\
> 	:pb#131072:bb#4096:fb#1024:\
> 	:pc#2698061:bc#8192:fc#1024:\
> 	:pd#844800:bd#8192:fd#1024:\
> 	:pe#844800:be#8192:fe#1024:\
> 	:pf#844621:bf#8192:ff#1024:\
> 	:pg#819200:bg#8192:fg#1024:\
> 	:ph#1715021:bh#8192:fh#1024:
> 
> Pretty high-tech stuff :-)
> 
> Simon.
> 

Wilko
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