1 - /BLOCK_SIZE

       /BLOCK_SIZE=512 (default)
       /BLOCK_SIZE=2048

    Specifies the target block size for the bootstrap device, in
    bytes.

    The 512-byte block size applies for most disk devices. The 2048-
    byte block size typically is used only when writing the boot
    block to specific OpenVMS Integrity servers CD and DVD devices.

2 - /I64

    Specifies OpenVMS Integrity servers as the target architecture
    for the boot block. The default boot file for OpenVMS Integrity
    servers is SYS$SYSROOT:[SYS$LDR]SYS$EFI.SYS.

3 - /PRESERVE

       /PRESERVE=keyword
       /PRESERVE=SIGNATURE

    /PRESERVE=SIGNATURE maintains the existing GUID disk signature
    value. The default is to generate a new signature for the target
    volume.

    SIGNATURE is the only keyword currently supported.