Hi Michael, Could you send us the doc link? Thanks a lot.
On Thu, Dec 6, 2012 at 6:47 AM, Michael Still <michael.st...@canonical.com>wrote: > On 12/05/2012 06:59 PM, Marco CONSONNI wrote: > > > To be honest it seems like I missed something because, from your > > investigation, the storage is kept under _base. Strange. I didn't know > that. > > Hi! The following description is libvirt specific. Bearing in mind that > this code is a moving target and has been re-written at least three > times in the last year [1], it works a bit like this... > > - you request an instance using a given image > - that image is fetched to _base from glance (if its not already there) > - that image is format converted if required, and then resized to the > requested size > - the instance disk image is a copy-on-write layer on top of that > resized image in _base and is stored in the instance's directory > - the instance is booted using the COW layer > > If another instance with the same image / disk size starts, it can short > circuit the process and use the already existing image, which is cool. > > When an instance is terminated, the instance directory is removed, but > files in _base remain. > > If you have image cache management turned on, then the files in _base > are periodically cleaned up. The files in _base are also checksummed to > try and detect file corruption, although that hasn't been the most loved > feature ever implemented. > > Hope this helps, > Michael > > 1: Several times I have gone to write a blog post about how this works, > and then realized the code has changed again. > > _______________________________________________ > Mailing list: https://launchpad.net/~openstack > Post to : openstack@lists.launchpad.net > Unsubscribe : https://launchpad.net/~openstack > More help : https://help.launchpad.net/ListHelp > -- Lei Zhang Blog: http://jeffrey4l.github.com twitter/weibo: @jeffrey4l
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