Device mappings in EC2

Kapil Thangavelu kapil.thangavelu at
Mon Jul 14 14:26:35 UTC 2014

On Mon, Jul 14, 2014 at 10:09 AM, Henning Eggers <henning at> wrote:

> Hi,
> this is a follow-up to these two:
> The new m3 EC2 instances come with fast SSD instance (ephemeral) storage
> volumes. To make these available, a device mapping has to be specified at
> instance launch time. AFAICT there is no such option in juju.
> On askubuntu Jorge suggests specifiying constraints in such a ways, that an
> old instance type is selected. In the LP bug on the other hand Kapil is
> calling for the complete removal of these old instance types. These two
> seem
> to be counter-productive. ;-)

> What I would need is a way to specify a device-mapping when launching a
> service or maybe a machine. I don't think it would make sense to change
> this
> on a per-unit base assuming that units are configured identically.
> Is there any solution for this in the pipeline?

my concern complaint on removal of old types was pre the ability to
actually specify what instance type you want as doing it via
cpupower/cores/mem/disk constraints was a confusing and indirect and often
needed source inspection to determine actual behavior. latest juju's now
allow directly specifying instance type, ie exactly what you want. i think
we should have a separate bug on the need for block dev mapping on these m3
instance types (juju does specify a block dev map when launching but
nothing specific around the m3 instance types).


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