lvm2/WHATS_NEW

Mondy 18th November 2002
========================

The new format of LVM metadata is ready for you to test!
  We expect it to be more efficient and more robust than the original format.
  It's more compact and supports transactional changes and replication.
  Should things go wrong on a system, it's human-readable (and editable).

Please report any problems you find to the mailing list, 
linux-lvm@sistina.com.  The software has NOT yet been thoroughly
tested and so quite possibly there'll still be some bugs in it.
Be aware of the disclaimer in the COPYING file.

While testing, we recommend turning logging on in the configuration file 
to provide us with diagnostic information:
  log {
        file="/tmp/lvm2.log"
	level=6
  }

You should schedule regular backups of your configuration file and
metadata backups and archives (normally kept under /etc/lvm).

Please read docs/example.conf and "man lvm.conf" to find out more about 
the configuration file.

To convert an existing volume group called vg1 to the new format using
the default settings, use "vgconvert -M2 vg1".  See "man vgconvert".

-M (or --metadatatype in its long form) is a new flag to indicate which
format of metadata the command should use for anything it creates.
Currently, the valid types are "lvm1" and "lvm2" and they can be
abbreviated to "1" and "2" respectively.  The default value for this
flag can be changed in the global section in the config file.

Backwards-compatible support for the original LVM1 metadata format is
maintained, but it can be moved into a shared library or removed
completely with configure's --with-lvm1 option.

Under LVM2, the basic unit of metadata is the volume group.  Different
volume groups can use different formats of metadata - vg1 could use
the original LVM1 format while vg2 used the new format - but you can't
mix formats within a volume group.  So to add a PV to an LVM2-format
volume group you must run "pvcreate -M2" on it, followed by "vgextend".

With LVM2-format metadata, lvextend will let you specify striping
parameters.  So an LV could consist of two or more "segments" - the
first segment could have 3 stripes while the second segment has just 2.

LVM2 maintains a backup of the current metadata for each volume group
in /etc/lvm/backup, and puts copies of previous versions in
/etc/lvm/archive.  "vgcfgbackup" and "vgcfgrestore" can be used to
create and restore from these files.  If you fully understand what 
you're doing, metadata can be changed by editing a copy of a current
backup file and using vgcfgrestore to reload it.

Please read the pvcreate man page for more information on the new
format for metadata.

All tools that can change things have a --test flag which can be used
to check the effect  of a set of cmdline args without really making the
changes.


What's not finished?
====================
The internal cache.  If you turn on debugging output you'll see lots of
repeated disk reads, many of which will eventually get optimised out.

--test sometimes causes a command to fail (e.g. vgconvert --test) even 
though the real command would work: again, fixing this is waiting for 
the work on the cache.

Several of the tools do not yet contain the logic to handle full
recovery: combinations of pvcreate and vgcfgrestore may sometimes be
needed to restore metadata if a tool gets interrupted or crashes or
finds something unexpected.  This applies particularly to tools that
work on more than one volume group at once (e.g. vgsplit).

Display output.  Some metadata information cannot yet be displayed.
Work has started on new display tools.

Recovery tools to salvage "lost" metadata directly from the disks:
but we hope the new format will mean such tools are hardly ever needed!