[Libvir] Re: parted/LVM for ET [Storage manager initial requirements and thoughts

[Daniel P. Berrange]

On Thu, Jun 14, 2007 at 05:55:33PM +0200, Jim Meyering wrote:
> "Richard W.M. Jones" <rjones at redhat.com> wrote:
> ...
> > From the virt-manager/libvirt p.o.v. it seems to me the important
> > operations are:
> >
> > (1) Find attached drives.
> >
> > (2) Find partitions available & their sizes.
> >
> > (3) Allocate logical volumes.
> >
> > (4) Find out how much free space is available on a partition, and
> > carve out a file.
> 
> How about creating a regular partition,
> or resizing an existing (non-LVM) file system?
> 
> > Correct me if I'm wrong (I usually am), but:
> >
> > Nothing can do (1) except doing a brute force scan over /dev and
> > looking for likely block devices (this is what vgscan does).
> >
> > Parted can do (2), with several limitations including sector size.  It
> > can't do (3) at all, but then neither can anything else except forking
> > the LVM command line tools.
> >
> > And (4) can be done by libvirtd using ordinary POSIX calls, so no
> > external library support is needed, just some work to remote those
> > operations (which is mostly done).
> 
> Isn't doing #4 portably pretty tricky?  There's still too much
> variation, because many of the details aren't covered by POSIX.
> At least for GNU df, it was -- it uses the mountlist module from gnulib:

We don't need to enumerate all the mount points. The admin will simply
configure particulra directories (eg /var/lib/xen/images) as storage
repositories. So we only need to be able to call statfs/statvfs on 
particular paths where we want to create a new image.

> Of course, if your target is just Linux, then it is easier.

Minimally we have to target Solaris too, since we know they already use
libvirt. 

Dan.
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