[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC V8 2/3] libxl domain snapshot API design
On Mon, Dec 08, 2014 at 11:12:14AM +0000, Wei Liu wrote: > On Mon, Dec 08, 2014 at 12:34:47AM -0700, Chun Yan Liu wrote: > > > > > > >>> On 12/6/2014 at 12:06 AM, in message > > <20141205160615.GA24938@xxxxxxxxxxxxxxxxxxxxx>, Wei Liu > > <wei.liu2@xxxxxxxxxx> > > wrote: > > > I have to admit I'm confused by the back and forth discussion. It's hard > > > to justify the design of new API without knowing what the constraints > > > and requirements are from your PoV. > > > > > > Here are my two cents, not about details, but about general constraints. > > > > > > There are two layers, one is user of libxl (clients -- xl, libvirt etc) > > > and libxl (the library itself). > > > > > > 1. it's better to *not* have storage management in libxl. > > > > > > It's likely that clients can have their own management functionality > > > already. I'm told that libvirt has that as well as XAPI. Having this > > > functionality in libxl is a bit redundant and requires lots of work > > > (enlighten libxl on what a disk looks like and call out to various > > > utilities). > > > > Thanks Wei and Ian for your reply. We did have much discussion around > > can/cannot (e.g. xl can finish disk snapshot?) and should/shouldnot > > (e.g. disk snapshot process should not in xl? domain_snapshot_delete > > should not in libxl?), and confusing because have different ideas. So, > > settling it down is helpful. > > > > Talking about libvirt, it does provide storage management but through > > storage pools and volumes. But usually, we don't use storage pool/vol > > but directly use backend files, then libvirt storage driver can not > > manage them. And for libvirt vol, functionality in storage driver is > > limited, at least 'snapshot' cannot be done. So, libvirt side also > > needs to add codes to handle disk snapshot, quite like xl does. > > > > OK, so I take it that libvirt can be completely out the picture? I mean, > it's not a requirement for you to integrate with libvirt? > > I was thinking a stack like this when I replied: > > libvirt: manages snapshot (including storage snapshot) > libxl > [other lower level stuffs] > > While I read from your reply, libvirt doesn't have that functionality > (or very limited), so you would like to do things like: > > libvirt (or your homebrew toolstack) > xl (xl or libxl manages domain snapshots) > libxl > [other lower level stuffs] > Note, I'm in no way endorsing this approach. This is my understanding (or misunderstanding) of what you intended to do. I started drawing pictures so that we can understand each other better. Wei. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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