[Libvir] Concepts in storage management

Daniel P. Berrange berrange at redhat.com
Tue Oct 16 18:08:37 UTC 2007

On Tue, Oct 16, 2007 at 05:16:33PM +0100, Richard W.M. Jones wrote:
> Daniel P. Berrange wrote:
> >On Tue, Oct 16, 2007 at 04:34:26PM +0100, Richard W.M. Jones wrote:
> >>Daniel P. Berrange wrote:
> >>>http://www.redhat.com/archives/libvir-list/2007-September/msg00119.html
> >>Since that thread is split across two months, can I bring to everyone's 
> >>attention the post I made yesterday:
> >>
> >>http://www.redhat.com/archives/libvir-list/2007-October/msg00057.html
> >>
> >>In particular the concept at the end that we shouldn't even try to 
> >>support every possible remote storage, but instead allow the 
> >>administrator to write "scriptlets" (small shell scripts with a 
> >>well-defined input & output) to perform a set of operations:
> >
> >This is really just an implementation detail. We still need to define the
> >storage concepts we want to expose in the public API, before figuring out
> >on the backend implementation. Most of the implementation wiill pretty 
> >much have to follow the scheme of just invoking command line tools like 
> >lvcreate
> >and lvs, since formal APIs are scarse.
> Well, a basic set of operations would be whatever we need to implement 
> virt-install/virt-manager remotely now, plus other suggestions as they 
> come along.
> From a fairly brief scan of the virt-install & virt-manager code that 
> would be:
>  - Create an empty a file with given name & size & sparseness.
>  - Detect if a named device or file exists (basically a remote stat).
>  - Copy image to remote temporary file (for kernel/CD-ROM).
>  - Check free space (remote statvfs).
> It might be nice to list LVs, but it doesn't seem to be necessary to 
> implement remote virt-* at the moment (AFAICS).

Current virt-manager doesn't enumerate block devices at all - it just
presents a file selection dialog rooted in /dev letting you select a
block device, be it a disk, or a logical volume. Using LVM volumes for
guests is probably more common  than using raw partitions based on user
reports i see.

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