parted/LVM for ET [Re: [Libvir] Storage manager initial requirements and thoughts
Daniel P. Berrange
berrange at redhat.com
Tue Mar 20 16:00:21 UTC 2007
On Tue, Mar 20, 2007 at 02:58:16PM +0000, David Edmondson wrote:
> On Tue, Mar 20, 2007 at 02:32:10PM +0000, Daniel P. Berrange wrote:
> > - There are a couple of different types of storage pool
> > - An LVM volume group
> > - Block devices
> > - A directory on a filesystem
> > - Each storage pool can have zero or more storage volumes allocated
> > - LVM volume group has multiple logical volumes
> > - Block device has multiple partitions
> > - A directory has multiple files (maybe sparse)
> > - Each storage pool has some measure of free space
> > - LVM volume group has unallocated physical extents
> > - Block device has unpartitioned sectors
> > - A directory has free space from underlying filesystem
> > - Every host has at least one storage pool with free space - ie a directory
> > on a filesystem. Some hosts may also have free LVM space, or unpartitioned
> > block devices but we can't assume their presence in general.
> ZFS takes a slightly different view:
> - ZFS storage pools are collections of physical devices (including
> data replication),
> - ZFS datasets are contained within ZFS storage pools and are
> either filesystems, volumes or snapshots.
> - ZFS filesystems are, well, filesystems,
> - ZFS volumes are available as block devices,
> - ZFS volumes can contain multiple partitions.
That all makes sense - the ZFS storage pools sounds like they provide
equivalent volume management capabilities to what you'd get in LVM.
> Currently we anticipate using both file-based images (inside ZFS and
> other filesystems) and ZFS volumes (to provide the impression of a
> dedicated physical device) for VMs, as well as dedicating real
> physical volumes, obviously.
> Overall this fits with your model, I think.
Yes, sounds just fine. On this subject, does ZFS come with any library API
for doing all the volume pool management tasks, or is it all just a set
of command line tools as we'd get with LVM ?
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