[Openstack-operators] Passing entire disks to instances

David Arroyo droyo at aqwari.net
Sat Aug 29 15:16:48 UTC 2015


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 

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.

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