Mount an Ebs Volume > 2Tb on Ubuntu 18.04

After a bit of experimentation, I can say that the answers to (1) and (2) are "yes" and "yes" — the only real problem is trying to use a large EBS volume as the root volume.

You can indeed mount a 16TB EBS volume without partitions, and Ubuntu 18.04 handles it without problems. Therefore, the easiest thing to do is to create a new, 16TB EBS volume, mount it on the EC2 instance, and copy over the data that you need.

First, you'll want to back up any data that you have on your current volume, just in case. To do this, you'll need to stop the EC2 instance (this is only necessary when snapshotting the root volume). Then, go to the Elastic Block Store Volumes page of the EC2 console, and choose "create snapshot" under "actions". Once finished, restart the EC2 instance. More details here.

1. Create an EBS volume in the AWS console, configure it with the size and type that you require (gpt3 is good for the specifications in the question, but see "Amazon EBS Volume Types" for more information), and attach it to your running instance. There's no need to stop the instance or touch its configuration at this point.

2. SSH into the EC2 instance and check that the volume is attached but not mounted:

   ubuntu:~$ lsblk
   NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
   loop1     7:1    0 55.4M  1 loop /snap/core18/1932
   loop2     7:2    0 97.9M  1 loop /snap/core/10583
   loop3     7:3    0 28.1M  1 loop /snap/amazon-ssm-agent/2333
   loop4     7:4    0 32.3M  1 loop /snap/amazon-ssm-agent/2996
   loop5     7:5    0 55.4M  1 loop /snap/core18/1944
   loop6     7:6    0 97.9M  1 loop /snap/core/10577
   xvda    202:0    0 15.6T  0 disk 
   └─xvda1 202:1    0    2T  0 part /
   xvdf    202:80   0   16T  0 disk 
   

   Notice that xvda (the root volume) has a partition underneath it (xvda1) and is mounted at /, whereas the new xvdf volume has neither partition nor mount point.

3. Fresh EBS volumes have no filesystem, so you need to create one: sudo mkfs -t xfs /dev/xvdf. Take care to reference the proper volume, otherwise you will overwrite data if you attempt to create a new filesystem on a volume which already contains one.

4. Create a place to mount the volume, I'll call it 'data': sudo mkdir /data.

5. Mount the volume, and you'll see it appear in the output of df. Optionally, update the fstab file to mount the volume automatically after reboot, as described here.

   ubuntu:~$ sudo mount /dev/xvdf /data
   ubuntu:~$ df -hT
   Filesystem     Type      Size  Used Avail Use% Mounted on
   udev           devtmpfs  7.4G     0  7.4G   0% /dev
   tmpfs          tmpfs     1.5G  828K  1.5G   1% /run
   /dev/xvda1     ext4      2.0T  1.8T  180G  91% /
   tmpfs          tmpfs     7.4G     0  7.4G   0% /dev/shm
   tmpfs          tmpfs     5.0M     0  5.0M   0% /run/lock
   tmpfs          tmpfs     7.4G     0  7.4G   0% /sys/fs/cgroup
   /dev/loop1     squashfs   56M   56M     0 100% /snap/core18/1932
   /dev/loop3     squashfs   29M   29M     0 100% /snap/amazon-ssm-agent/2333
   /dev/loop4     squashfs   33M   33M     0 100% /snap/amazon-ssm-agent/2996
   tmpfs          tmpfs     1.5G     0  1.5G   0% /run/user/1000
   /dev/loop5     squashfs   56M   56M     0 100% /snap/core18/1944
   /dev/loop6     squashfs   98M   98M     0 100% /snap/core/10577
   /dev/loop2     squashfs   98M   98M     0 100% /snap/core/10583
   /dev/xvdf      xfs        16T   17G   16T   1% /data
   

6. Finally, set the file permissions you need for /data and copy over any files that you would like on the new drive. Consider using rsync here as a less brittle alternative to cp.