gistfile1.txt

$ dd if=/dev/zero of=./small.ext4 bs=1000000 count=100
$ dd if=/dev/zero of=./medium bs=1000000 count=50
$ mkfs.ext4 ./small.ext4
$ sudo mkdir /mnt/tmp 
$ sudo mount -o loop ./small.ext4 /mnt/tmp
$ sudo chmod a+rxw /mnt/tmp 
$ sftp localhost 
sftp> put medium /mnt/tmp/a
sftp> put medium /mnt/tmp/b
sftp> put medium /mnt/tmp/b

$ ls -la /mnt/tmp

drwxrwxrwx 3 root  root      1024 Aug 29 14:33 .
drwxr-xr-x 6 root  root      4096 Aug 29 11:07 ..
-rw-rw-r-- 1 slacy slacy 50000000 Aug 29 14:33 a
-rw-rw-r-- 1 slacy slacy 36032512 Aug 29 14:33 b
-rw-rw-r-- 1 slacy slacy        0 Aug 29 14:33 c
drwx------ 2 root  root     12288 Aug 29 11:07 lost+found