I created an EBS volume (100GB) from a snapshot (10GB), but when I attach the volume to an instance and mount it as /vol, then I check with df -h, I see that /vol has size of 10GB although it's a 100GB disk. What's wrong with my procedure ? Thank you!
The volume is 100GB, but the filesystem is still only 10GB.
You need to grow/expand the filesystem to fill the rest of the space on the disk volume.
The method you use to do this depends on what type of filesystem you're running on this volume.
If you're running an ext3 filesystem, it's as simple as:
$ resize2fs /dev/xvdX
(replace xvdX with the correct device name for the volume)