I work on an Amazon EC2 instance that somebody else set up. We have an EBS volume mounted on /dev/sda, even though the root device is already on /dev/sda1, and we're also using `/dev/sda2'

user@server:~$ mount
/dev/sda1 on / type ext3 (rw)
... (snip)
/dev/sda2 on /mnt type ext3 (rw)
/dev/sda on /vol type xfs (rw,noatime)
...

This doesn't seem to fit with what I know about the way /dev/ works. How is this possible, and more importantly: will this cause trouble in the future?

I'm running ubuntu 9.04 jaunty.