sudo umount /dev/mapper/teststop
sudo dmsetup remove teststop

echo 0 `sudo blockdev --getsz /dev/sdb` linear /dev/sdb 0 |sudo dmsetup create teststop
sudo mount /dev/mapper/teststop /mnt/test/ -o data=ordered,barrier=1,commit=300 #,noauto_da_alloc
/home/andres/src/postgresql/src/backend/postgres -D /mnt/test/pg/
#Here we got stopped after a crash
sudo umount /dev/mapper/teststop
sudo dmsetup remove -f teststop
echo "crashed?"

#Here the device is completely gone, so were in the same situation as
#if we had crashed and are restarting
echo 0 `sudo blockdev --getsz /dev/sdb` linear /dev/sdb 0 |sudo dmsetup create teststop
sudo mount /dev/mapper/teststop /mnt/test/ -o data=ordered,barrier=1,commit=300 #,noauto_da_alloc
/home/andres/src/postgresql/src/backend/postgres -D /mnt/test/pg/

sudo umount /dev/mapper/teststop
sudo dmsetup remove teststop