How to figure out where is an UNKNOWN attached Disk/Volume coming from?

On CentOS 6 on AWS/EC2, how do I figure out where is a particular Disk or Volume coming from? I'm trying to figure out the disk xvdf here, which is NOT part of the attached Volumes (EBS) table.

In other words, I don't know where is this Disk/Volume xvdf coming from.

[root@ec2-server /]# lsblk 
NAME MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvdf 202:80   0 37.5G  0 disk 
xvdk 202:160  0   50G  0 disk /backups
xvdj 202:144  0  100G  0 disk /glusterfs
xvde 202:64   0    8G  0 disk /

[root@ec2-server /]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/xvde       7.8G  5.5G  2.0G  74% /
tmpfs           7.2G     0  7.2G   0% /dev/shm
/dev/xvdj       100G   65G   36G  65% /glusterfs
/dev/xvdk        50G   52M   47G   1% /backups
gluster1:/gv0   100G   65G   36G  65% /var/www/html

[root@ec2-server /]# fdisk -l

Disk /dev/xvdf: 40.3 GB, 40256929792 bytes
255 heads, 63 sectors/track, 4894 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000
..

Again, it was not mounted, and hence not in the output of # mount -s command. (When I then mounted it and tried to inspect the contents inside, it is kinda blank inside.)

Then again, while looking at the EC2 Volume attachment info, the xvdf is NOT part of the attachment list. The 3 Volumes shown in the list are xvde (8GB), xvdj (100GB) and xvdk (50GB) respectively inside the Server, which I was aware of.

I also used the AWS CLI command # aws ec2 describe-volumes --filters Name=attachment.instance-id,Values=i-XXXXXXXX. And it still returns the same 3 Volumes as in the screenshot above. The xvdf is still not listed there.

That means, I didn't attach this particular xvdf Disk or Volume. And hence don't know where is it coming from.

Please advise how to figure this out further.

Note: It's been quite a while since I last did the disk related stuffs (attached disks, etc) on that Server. Therefore, I'm now finding it difficult to recall what was it. Or rather, more concerned about whose disk it is, and why it is here.