small-volume control first:
open: No such file or directory
now the paced 4GiB growth on BIG:
stepped to 4032MiB; final ftruncate 0x100010000:
before: size 4227858432
ftruncate(0x100010000) OK; in-memory size now 4295032832 (0x100010000)
NOTE: size exceeds MSDOSFS_FILESIZE_MAX (0xFFFFFFFF); dirent field is 32-bit
size now:
size=4295032832
remount:
size-after-remount=65536
-rwxr-xr-x  1 root  wheel  65536 Oct 25 10:34 /mnt/df3159/BIG
DONE-DF3159
open: No such file or directory
posix wants EFBIG (file too large); got the above