An option is to replace the actual SCSI Disk Drive with a
SCSI2SD adapter that uses a SD memory card as the storage
media.  This appears to be a common way to replace old
small, e.g. < 10 GByte,  SCSI hard drives.   Rev 9-Aug-22



http://www.nextcomputers.org/forums/index.php?topic=3737.0

http://www.nextcomputers.org/forums/index.php?topic=4728.0

www.codesrc.com/mediawiki/index.php/SCSI2SD

ctrl-alt-rees.com/2018-09-19-nextstation-easy-scsi2sd-setup.html

Winworldpc.com/product/nextstep/3x



Example setup of the scsi2sd card:


<SCSI2SD>
    <BoardConfig>
        <unitAttention>false</unitAttention>
        <parity>false</parity>
        <!-- ********************************************************
        Only set to true when using with a fast SCSI2 host
         controller. This can cause problems with older/slower
         hardware.
        ********************************************************* -->
        <enableScsi2>true</enableScsi2>
        <!-- ********************************************************
        Setting to 'true' will result in increased performance at the
        cost of lower noise immunity.
        Only set to true when using short cables with only 1 or two
        devices. This should remain off when using external SCSI1 DB25
        cables.
        ********************************************************* -->
        <disableGlitchFilter>false</disableGlitchFilter>
        <enableCache>false</enableCache>
        <enableDisconnect>false</enableDisconnect>
        <!-- ********************************************************
        Respond to very short duration selection attempts. This supports
        non-standard hardware, but is generally safe to enable.
        Required for Philips P2000C.
        ********************************************************* -->
        <selLatch>false</selLatch>
        <!-- ********************************************************
        Convert luns to IDs. The unit must already be configured to respond
        on the ID. Allows dual drives to be accessed from a
        XEBEC S1410 SASI bridge.
        eg. Configured for dual drives as IDs 0 and 1, but the XEBEC will
        access the second disk as ID0, lun 1.
        See ttp://bitsavers.trailing-edge.com/pdf/xebec/104524C_S1410Man_Aug83.pdf
        ********************************************************* -->
        <mapLunsToIds>false</mapLunsToIds>
    </BoardConfig>
    <SCSITarget id="3">
        <enabled>true</enabled>
        <!-- ********************************************************
        Space separated list. Available options:
        apple      Returns Apple-specific mode pages
        ********************************************************* -->
        <quirks></quirks>
        <!-- ********************************************************
        0x0    Fixed hard drive.
        0x1    Removable drive.
        0x2    Optical drive  (ie. CD drive).
        0x3    1.44MB Floppy Drive.
        ********************************************************* -->
        <deviceType>0x0</deviceType>
        <!-- ********************************************************
        Device type modifier is usually 0x00. Only change this if your
        OS requires some special value.
        0x4C    Data General Micropolis disk
        ********************************************************* -->
        <deviceTypeModifier>0x0</deviceTypeModifier>
        <!-- ********************************************************
        SD card offset, as a sector number (always 512 bytes).
        ********************************************************* -->
        <sdSectorStart>0</sdSectorStart>
        <!-- ********************************************************
        Drive geometry settings.
        ********************************************************* -->
        <scsiSectors>4194303</scsiSectors>
        <bytesPerSector>512</bytesPerSector>
        <sectorsPerTrack>139</sectorsPerTrack>
        <headsPerCylinder>4</headsPerCylinder>
        <!-- ********************************************************
        Drive identification information. The SCSI2SD doesn't
        care what these are set to. Use these strings to trick a OS
        thinking a specific hard drive model is attached.
        ********************************************************* -->
        <!-- 8 character vendor string -->
        <!-- For Apple HD SC Setup/Drive Setup, use 'SEAGATE' -->
        <vendor>codesrc</vendor>
        <!-- 16 character produce identifier -->
        <!-- For Apple HD SC Setup/Drive Setup, use 'ST225N' -->
        <prodId>SCSI2SD</prodId>
        <!-- 4 character product revision number -->
        <!-- For Apple HD SC Setup/Drive Setup, use '1.0 ' -->
        <revision> 4.2</revision>
        <!-- 16 character serial number -->
        <serial>1234567812345678</serial>
    </SCSITarget>
    [...other targets omitted, are switched off...]
</SCSI2SD>


Then the xml config can be programmed into the SCSI2SD by
plugging it in to a host computer using a Mini USB cable,
running  scsi2sd-util,  and using the “Open File” and
“Save To Device” options in the File menu.



Example of loading the operating system onto the scsi2sd:


sudo  dd  if=NS33_2GB.dd  of=/dev/mmcblk0  conv=fdatasync

The conv=fdatasync flag just skips the disk buffer in Linux
and writes to the device directly, ensuring everything gets
written and skipping the lengthy wait when ejecting the SD
card.