[openstack-dev] [Keystone] [Glance] Centralizing Quotas and New Quotas in Glance

Mark Washenberger mark.washenberger at markwash.net
Tue Apr 30 15:35:42 UTC 2013

Hi all,

During the summit there was some discussion about centralizing quotas to
ease administration and support domain-level quotas that would span
endpoints (i.e. you might have a Nova instance limit of 10 that is met when
you have 2 instances in Region East and 8 instances in Region West.)

As a brief summary, this was my estimate of the reception of the various
levels of centralization that were discussed:

1) Central administration of quota limits - very high level of support
2) Central storage of quota limits - high level of support, some notable
3) Central tracking of quota usage - no consensus
4) Central enforcement of quota limits - virtually no support, consensus
against this approach

As we are looking at adding quotas to Glance during Havana, I have a few
questions about this effort.

- Who is planning work on centralized quotas during Havana and when/where
are any discussions about this work happening? Are there any series targets

- If central storage of quota limits is to be adopted, do we plan for
quotas to lose some of their consistency? To explain, right now, quotas are
fairly consistent--if my limit is 10 instances, its very difficult for me
to end up with 11 instances, even if my limit just recently changed. But if
limits are stored elsewhere, there may be an accepted propagation delay
that would make it possible to unintentionally violate my quota.

- If losses to the consistency of quotas are not acceptable, what are the
performance implications of Nova having to call out to another service to
determine a quota limit prior to completing a server create request? (This
part sounds scary to me!)

Thanks for your help!
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