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 -=|