Thanks to 
wilms_at_astro.uni-tuebingen.de
olle_at_cb.uu.se
hagan_at_cih.com 
sarasin_at_yosemite.cop.dec.com
buhs_at_cs.usask.ca
szgyula_at_skysrv.Pha.Jhu.EDU
alan_at_nabeth.cxo.dec.com
who answer my question :
>Does anyone have /etc/disktab entries for QUANTUM _EMPIRE_2100S(2.1GB)
>and  QUANTUM-XP34301-1051 4.1GB disks
>for the first disk I am interesting also for Ultrix as well.
the soluthion is that: 
        
        Digital UNIX and ULTRIX V4.0 and later can get the
        geometry information directly from the disk, without
        the need for a disktab entry.  The driver supplies
        a default partition table.  For ULTRIX and disks larger
        than 2 GB, the partition table will need to be customized.
        On Digital UNIX to take advantage of the feature:
                disklabel -wr /dev/rrz#c some-name
        On ULTRIX one of:
                newfs /dev/rrz#c some-name
        or:
                newfs /dev/rrz#c /dev/rrz#c
Received on Thu Dec 07 1995 - 11:23:31 NZDT