SGIVOL_NBTOOL_NTRACKS
if (st.st_size < (SGIVOL_NBTOOL_NSECS * SGIVOL_NBTOOL_NTRACKS))
SGIVOL_NBTOOL_NSECS * SGIVOL_NBTOOL_NTRACKS);
htobe16(st.st_size / (SGIVOL_NBTOOL_NSECS * SGIVOL_NBTOOL_NTRACKS));
volhdr->dp.dp_trks0 = htobe16(SGIVOL_NBTOOL_NTRACKS);