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 ? Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|