Comment 1 for bug 458850

This is just to collect information about ephemeral storage on UEC and
ec2.

on ec2, instance types are described at:
http://docs.amazonwebservices.com/AWSEC2/latest/DeveloperGuide/index.html?instance-types.html

type | arch | ephemeral disk| mounted ?
-----------------------------------------------
m1.small | i386 | 150G sda2 ___ | sda2 -> /mnt
c1.medium | i386 | 340G sda2 ___ | sda2 -> /mnt
m1.large | amd64| 420G sd[bc] _ | sdb -> /mnt
m1.xlarge | amd64| 420G sd[bcde] | sdb -> /mnt
c1.xlarge | amd64| 420G sd[bcde] | sdb -> /mnt

The above can be summed up as:
if arch is i386, there is a single device, and that is sda2
if arch is amd64, there is more than 1 device, vmbuilder writes /etc/fstab
that mounts the first (sdb) to /mnt

on Eucalyptus, the available ephemeral disks depends on configuration.
The storage available to an instance depends on the configuration of its
instance type. If the configured storage amount is greater than the size
of the root filesystem, then the instance will have access to a partition
in /dev/sda2 that has a size of (config_value - root_size - swap_size).

In all cases on eucalyptus, /dev/sda2 contains an empty ext2 the filesystem.

Some other things to note:
* In all cases UEC and EC2, /dev/sda1 is a filesystem the size of the
  registered image, and is mounted on /
* In EUC, ephemeral storage is a ext2 filesystem. In ec2, it is ext3.
* on ec2, i686 instances have a ~ 1G swap partition on /dev/sda3
* I'm not exactly certain on how swap_size (in Euca) is determined. in
  default config of m1.small, there is ~ 650M partition for swap (663212
  blocks).