I have my db kept at /mnt, using ephemeral storage that comes with ec2 instance. To take the backup using ec2 api tools we need a volume id, but in the aws console I can fin
If you are able to configure a software RAID mirror, you can attach an EBS-backed disk to the instance, configure a mirror, then wait for replication to complete. I have successfully used this method to move "ephemeral" data into EBS after I had already created the instance (and I did not want to shut down and reboot).
Once you have the data on EBS, back up with EBS images.
This method works particularly well when you have multiple copies of the data running on different identical instances, but you only need one of them persisted to EBS (in my case, using Couchbase server, the CB data was on ephemeral drives, but I had one of the instances mirrored to EBS such that all the data on my cluster ended up in EBS).