Set reserved_host_memory_mb to zero for vCenter deployment

[Andrey Danin]

Affecting 5.0, 5.0.1, 5.1, and 6.0 releases.

Vmware recommends [0] to set nova-scheduler’s option ‘reserved_host_memory_mb’ to 0 (Fuel uses a default value which is 512). That’s because vCenter is already doing a memory reservation and there is no valuable reason to do it twice. vCenter provides an aggregated memory from all ESXi’s in a vSphere cluster, and this option is applied to a cumulative value not to each individual ESXi node. So, actually, we looses 512MB for each vSphere cluster.

But because it’s a global configuration option it potentially can cause some problems in a multi-HV environment. We can look for a better solution in this case. For instance, set ‘reserved_host_memory_mb’ to 0 anyway, but force non-vCenter nova-computes provide an already adjusted memory value.

[0] http://docs.openstack.org/trunk/config-reference/content/vmware.html#VMwareVCDriver_configuration_options

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/131140

[OpenStack Infra (hudson-openstack)]

Change abandoned by Igor Zinovik (<email address hidden>) on branch: master
Review: https://review.openstack.org/131140

[Igor Gajsin (igajsin)]

We can't fix it due to soft code freeze. Postpone to 8.0.

[Bug Checker Bot (bug-checker)]

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[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/301550

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/301550
Committed: https://git.openstack.org/cgit/openstack/fuel-library/commit/?id=43eadba18974b93cb3a89e6611237a4902c57592
Submitter: Jenkins
Branch: master

commit 43eadba18974b93cb3a89e6611237a4902c57592
Author: Alexander Arzhanov <email address hidden>
Date: Tue Apr 5 09:51:47 2016 +0000

    Set reserved host memory to 0MB for nova-compute with VCDriver

    The reserved_host_memory_mb option value is 512 MB by default.
    However, VMware recommends that you set this option to 0 MB
    because the vCenter driver reports the effective memory
    available to the virtual machines.
    Link to review for openstack doc(VMware recommends):
    https://review.openstack.org/#/c/73450/2

    Change-Id: I9ab240820740ed3ecd09fc7ccdc5109875baf453
    Closes-bug: #1382539

[Ilya Bumarskov (ibumarskov)]

Verified on Fuel 9.0 mos-iso#465

root@node-5:~# grep -r "reserved_host_memory_mb" /var/log
/var/log/puppet.log:2016-06-14 18:11:24 +0000 /Stage[main]/Nova::Compute/Nova_config[DEFAULT/reserved_host_memory_mb]/ensure (notice): created
/var/log/nova/nova-compute.log:2016-06-14 18:12:50.133 26361 DEBUG oslo_service.service [req-0429de39-c9b5-4ed9-957d-4dd50e1be67c - - - - -] reserved_host_memory_mb = 0 log_opt_values /usr/lib/python2.7/dist-packages/oslo_config/cfg.py:2517
/var/log/nova/nova-compute.log:2016-06-14 18:13:11.823 29054 DEBUG oslo_service.service [req-1bf53aa7-a9af-4da7-a9e4-0a176ab748d7 - - - - -] reserved_host_memory_mb = 0 log_opt_values /usr/lib/python2.7/dist-packages/oslo_config/cfg.py:2517
/var/log/nova-all.log:<183>Jun 14 18:12:50 node-5 nova-compute: 2016-06-14 18:12:50.133 26361 DEBUG oslo_service.service [req-0429de39-c9b5-4ed9-957d-4dd50e1be67c - - - - -] reserved_host_memory_mb = 0 log_opt_values /usr/lib/python2.7/dist-packages/oslo_config/cfg.py:2517
/var/log/nova-all.log:<183>Jun 14 18:13:11 node-5 nova-compute: 2016-06-14 18:13:11.823 29054 DEBUG oslo_service.service [req-1bf53aa7-a9af-4da7-a9e4-0a176ab748d7 - - - - -] reserved_host_memory_mb = 0 log_opt_values /usr/lib/python2.7/dist-packages/oslo_config/cfg.py:2517