Just some more data, collected from oneiric builds of 20110601 (Ubuntu 2.6.39-3.10-virtual 2.6.39)
i386-t1.micro: block-device-mapping: {'ami': '/dev/sda1', 'ephemeral0': '/dev/sdb', 'root': '/dev/sda1'} /proc/partitions: xvde1
i386-m1.small-ebs: block-device-mapping: {'ami': '/dev/sda1', 'ephemeral0': '/dev/sda2', 'root': '/dev/sda1', 'swap': 'sda3'} /proc/partitions: xvde1 xvde2 xvde3
i386-m1.small-instance: block-device-mapping: {'ami': 'sda1', 'ephemeral0': 'sda2', 'root': '/dev/sda1', 'swap': 'sda3'} /proc/partitions: xvde1 xvde2 xvde3
amd64-m1.large-ebs: block-device-mapping: {'ami': '/dev/sda1', 'ephemeral0': '/dev/sdb', 'root': '/dev/sda1'} /proc/partitions: xvde1 xvdf
amd64-m1.large-instance: block-device-mapping: {'ami': 'sda1', 'ephemeral0': 'sdb', 'ephemeral1': 'sdc', 'root': '/dev/sda1'} /proc/partitions: xvde1 xvdf xvdg
So, it looks like basically the kernel is starting its enumerating with xvde.
Just some more data, collected from oneiric builds of 20110601 (Ubuntu 2.6.39-3.10-virtual 2.6.39)
i386-t1.micro: device- mapping: {'ami': '/dev/sda1', 'ephemeral0': '/dev/sdb', 'root': '/dev/sda1'}
block-
/proc/partitions: xvde1
i386-m1.small-ebs: device- mapping: {'ami': '/dev/sda1', 'ephemeral0': '/dev/sda2', 'root': '/dev/sda1', 'swap': 'sda3'}
block-
/proc/partitions: xvde1 xvde2 xvde3
i386-m1. small-instance: device- mapping: {'ami': 'sda1', 'ephemeral0': 'sda2', 'root': '/dev/sda1', 'swap': 'sda3'}
block-
/proc/partitions: xvde1 xvde2 xvde3
amd64-m1.large-ebs: device- mapping: {'ami': '/dev/sda1', 'ephemeral0': '/dev/sdb', 'root': '/dev/sda1'}
block-
/proc/partitions: xvde1 xvdf
amd64-m1. large-instance: device- mapping: {'ami': 'sda1', 'ephemeral0': 'sdb', 'ephemeral1': 'sdc', 'root': '/dev/sda1'}
block-
/proc/partitions: xvde1 xvdf xvdg
So, it looks like basically the kernel is starting its enumerating with xvde.