cinder/releasenotes/notes/vmware_enable_volume_stats-...

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---
upgrade:
- |
VMware vmdk driver: The vmware vmdk driver had its get_volume_stats
removed in a previous release due to a potential performance hit of 20%
at a high load. The problem with reporting ``unknown`` back to the
scheduler, is that it effectively removes cinder's ability to properly
schedule based on capacity utilization. When this driver is enabled in a
heterogenous environment without properly reporting utilization
statistics, the scheduler's capacity filter will always allow this driver
to service a provisioning request. Without reporting the backend stats,
the capacity filter also can't determine the reserved_percentage as well
as the max_over_subscription_ratio. To enable the collection of stats
set ``vmware_enable_volume_stats`` to True in the driver section of
cinder.conf. The default setting is False. Keep in mind that there may
be a degradation in performance on the vcenter when enabling this setting.
fixes:
- |
VMware vmdk driver: The collection of volume stats, which had been
disabled, may now be turned on by using the ``vmware_enable_volume_stats``
configuration option. The default for this option is False (no
stats collection). Be aware that enabling volume stats may cause
performance issues under high load.