[openstack-dev] A simple way to improve nova scheduler

Boris Pavlovic boris at pavlovic.me
Fri Jul 19 14:52:55 UTC 2013

Hi all,

In Mirantis Alexey Ovtchinnikov and me are working on nova scheduler

As far as we can see the problem, now scheduler has two major issues:

1) Scalability. Factors that contribute to bad scalability are these:

*) Each compute node every periodic task interval (60 sec by default)
updates resources state in DB.

*) On every boot request scheduler has to fetch information about all
compute nodes from DB.

2) Flexibility. Flexibility perishes due to problems with:

*) Addiing new complex resources (such as big lists of complex objects e.g.
required by PCI Passthrough

*) Using different sources of data in Scheduler for example from cinder or

(as required by Volume Affinity Filter

We found a simple way to mitigate this issues by avoiding of DB usage for
host state storage.

A more detailed discussion of the problem state and one of a possible
solution can be found here:


Best regards,

Boris Pavlovic

Mirantis Inc.
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