[cs615asa] Availability Zones of Volumes and Instances

[Jan Schaumann]

Tejas <tnadkarn at stevens.edu> wrote:
> How is everyone handling this issue? I can check the zone of the  
> instance and create a volume in that zone fine no issue. But if the user  
> wants to use an existing volume and then creates a new instance there's  
> no way in the design of ec2-start-instance to specify a zone so I can  
> make sure they're in the same zone.

Good thinking!  It's an interesting problem that clearly wasn't
immediately visible from the project requirements, so you have a few
options to choose from (and neither one is necessarily "better" or the
correct solution).

> Can we modify the ec2-start-instance to provide a way to specify a zone?

That is one way to solve this.

Also, since ec2-start-instance honors the environment variable
EC2_RUN_INSTANCES_FLAGS, the user can already specify a preferred zone
herself.  So you can also make the decision to push this on the user and
simply say that if a user specifies an instance or volume, than she
better have made sure that the zones match.  In that case, it'd be
useful for your tool to alert if that is not the case (or otherwise
generate a useful error).

-Jan