Nova loads images on demand from Glance, which may then be shared by multiple VMs via copy on write layers. This resulting image cache on each compute server is currently unmanaged, and performing any audit / clean-up operations on it over a lagre number of compute servers is a non trivial opertaional procedure. This session would explore the concept of a cache manager to identify the list of images and thier current state with respect to thier usage by VMs and if they still exist on glance. Based on this state of cached images the cache manager would be able to take a number of configurable actions, such as: - Deleteing images in the cache that are no longer used (or have not been used for some period) by VMs - Deleteing images in the cache that are no longer uesd by VMs and are no longer present in Glance - Preloading specific images, for example by matching on specific Glance Metadata - By refering to meta-data associated with the images track the usage of licenced Operating Systems Preloading will need to need to implement a mechanism to ensure that compute servers do not all request the same image from glance concurrently. Once image state data is available it could be used by an scheduler enhancment to place VMs on servers which already have a cached copy of the required image
Tuesday October 4, 2011 5:30pm - 5:55pm EDT
Hutchinson
