title: Google Cloud attached disk size incorrect
body: <p>I'm trying to create a compute instance on Google Cloud with a 20TB disk attached, but I'm seeing something strange.  When I specify the size of the disk size in the gcloud command I do not see that same disk size reflected when I check the size of the instance.  I've also tried creating new disks and attaching them, resizing the attached disks, but it does not go about 2TB.  Is 2TB the max disk size for compute instances?</p>
  
  <pre><code>$ gcloud compute instances create instance --boot-disk-size 10TB --scopes storage-rw
  Created [https://www.googleapis.com/compute/v1/projects/project/zones/us-central1-a/instances/instance].
  NAME    ZONE           MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP     STATUS
  instance  us-central1-a  n1-standard-1               10.240.0.2   104.154.45.175  RUNNING
  $ gcloud compute ssh gm-vcf
  Warning: Permanently added 'compute.8994721896014059218' (ECDSA) to the list of known hosts.
  
  The programs included with the Debian GNU/Linux system are free software;
  the exact distribution terms for each program are described in the
  individual files in /usr/share/doc/*/copyright.
  
  Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
  permitted by applicable law.
  
  user@instance:~$ df -h
  Filesystem      Size  Used Avail Use% Mounted on
  /dev/sda1       2.0T  880M  1.9T   1% /
  udev             10M     0   10M   0% /dev
  tmpfs           743M  8.3M  735M   2% /run
  tmpfs           1.9G     0  1.9G   0% /dev/shm
  tmpfs           5.0M     0  5.0M   0% /run/lock
  tmpfs           1.9G     0  1.9G   0% /sys/fs/cgroup
  </code></pre>