Open Stack

Hello,

I would like to pass entire disks to my openstack instances. I have 
some IO-bound workloads and would like to avoid any overhead or 
contention by giving an instance access to N additional disks, such 
that they do not share that disk with other guests on the same compute 
node.

These additional disks do not need to last longer than the instances 
themselves; they are "ephemeral" in that regard. There is no need for 
backup, no need for instance or data migration, and no need for running 
the instance on a separate compute node from the extra disks. 
Effectively I want to have an "extra disks" property, as part of a 
flavor or image, that is handled like vcpus without overcommit.

I have been doing some research but have not yet found an obvious way 
to do this in openstack. Does anyone else have a similar use case, and 
how have you handled it? To be more specific, we run some very large 
Cassandra clusters on physical hardware, with excellent performance. 
Cassandra is largely IO-bound, and we want to virtualize it without 
introducing unnecessary IO latency.

Cheers,
David
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