Dependancies :
==============

These libs have been dropped in the multipath tree :
  
o libdevmapper : comes with device-mapper-XXXX.tar.gz
  See www.sistina.com
o libsysfs : comes with sysutils or udev
  See ftp.kernel.org/pub/linux/utils/kernel/hotplug/
o klibc
  See ftp.kernel.org/pub/linux/libs/klibc/

External :

o Linux kernel 2.6.10-rc with udm2 patchset (or greater)
  ftp://sources.redhat.com/pub/dm/
  
How it works :
==============

Get a path list in sysfs.

For each path, a wwid is retrieved by a callout program.
Only White Listed HW can retrieve this info.

Coalesce the paths according to pluggable policies and store
 the result in mp array.

Feed the maps to the kernel device mapper.

The naming of the corresponding block device is handeld 
by udev with the help of the devmap_name proggy. It is 
called by the following rule in /etc/udev/udev.rules :

KERNEL="dm-[0-9]*", PROGRAM="/sbin/devmap_name %M %m", \
NAME="%k", SYMLINK="%c"

Notes :
=======

o 2.4.21 version of DM does not like even segment size.
  if you enconter pbs with this, upgrade DM.

Credits :
=========

o Heavy cut'n paste from sg_utils. Thanks goes to D. 
  Gilbert.
o Light cut'n paste from dmsetup. Thanks Joe Thornber.
o Greg KH for the nice sysfs API.
o The klibc guys (Starving Linux Artists :), espacially
  for their nice Makefiles and specfile
