On 20 Sep 2016, at 16:38, Sean Dague <s...@dague.net<mailto:s...@dague.net>> wrote: ... There were also general questions about what scale cells should be considered at.
ACTION: we should make sure workarounds are advertised better ACTION: we should have some document about "when cells"? This is a difficult question to answer because "it depends." It's akin to asking "how many nova-api/nova-conductor processes should I run?" Well, what hardware is being used, how much traffic do you get, is it bursty or sustained, are instances created and left alone or are they torn down regularly, do you prune your database, what version of rabbit are you using, etc... I would expect the best answer(s) to this question are going to come from the operators themselves. What I've seen with cellsv1 is that someone will decide for themselves that they should put no more than X computes in a cell and that information filters out to other operators. That provides a starting point for a new deployment to tune from. I don't think we need "don't go larger than N nodes" kind of advice. But we should probably know what kinds of things we expect to be hot spots. Like mysql load, possibly indicated by system load or high level of db conflicts. Or rabbit mq load. Or something along those lines. Basically the things to look out for that indicate your are approaching a scale point where cells is going to help. That also helps in defining what kind of scaling issues cells won't help on, which need to be addressed in other ways (such as optimizations). -Sean We had an ‘interesting' experience splitting a cell which I would not recommend for others. We started off letting our cells grow to about 1000 hypervisors but following discussions in the large deployment team, ended up aiming for 200 or so per cell. This also allowed us to make the hardware homogeneous in a cell. We then split the original 1000 hypervisor cell into smaller ones which was hard work to plan. Thus, I think people who think they may need cells are better adding new cells than letting their first one grow until they are forced to do cells at a later stage and then do a split. Tim -- Sean Dague http://dague.net __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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