红帽全球峰会10.4. 配置 nova-cache 清理
当出现以下任一条件满足时，后台进程会定期运行，以从 nova 缓存中删除镜像：
- 该镜像没有被实例使用。
-
镜像的年龄大于 nova 参数
remove_unused_original_minimum_age_seconds的值。
remove_unused_original_minimum_age_seconds 参数的默认值为 86400。该值以秒为单位表示，等于 24 小时。您可以在初始部署期间，或使用 NovaImageCachTTL tripleo-heat-templates 参数或云堆栈更新期间控制这个值：
parameter_defaults:
NovaImageCacheTTL: 604800 # Default to 7 days for all compute roles
Compute2Parameters:
NovaImageCacheTTL: 1209600 # Override to 14 days for the Compute2 compute role
parameter_defaults:
NovaImageCacheTTL: 604800 # Default to 7 days for all compute roles
Compute2Parameters:
NovaImageCacheTTL: 1209600 # Override to 14 days for the Compute2 compute role
当您指示 playbook 预缓存 Compute 节点上已存在的镜像时，ansible 不会报告更改，但镜像的年龄被重置为 0。运行 ansible play 比 NovaImageCacheTTL 参数的值更频繁，以维护镜像的缓存。
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