Description of problem:
Installation uses a custom partition layout.  The anaconda installer detects all pre-existing software raid arrays and LVMs, but only dynamically assembles the raid arrays the user chooses to install on.

Version-Release number of selected component (if applicable):
RHEL 6.1 anaconda installer

How reproducible:
very

Steps to Reproduce:
1. create a software raid array and an LVM over it
2. don't use it (i.e. don't assign any path like / or /opt or anything to it)
3. install, wait for last stage (installing grub)
  
Actual results:
RuntimeError: get_sysfs_path_by_name: Could not find sysfs path for '/dev/md2' (it is not at '/sys/class/block/md2')

Expected results:
Successful install

Additional info:
RuntimeError: get_sysfs_path_by_name: Could not find sysfs path for '/dev/md2' (it is not at '/sys/class/block/md2')
</binding><binding fileName="/tmp/anaconda-tb-UqOnrG" name="pythonUnhandledException" type="text">anaconda 13.21.117 exception report
Traceback (most recent call first):
  File "/usr/lib/anaconda/iutil.py", line 805, in get_sysfs_path_by_name
    "for '%s' (it is not at '%s')" % (dev_node, dev_path))
  File "/usr/lib/anaconda/storage/formats/__init__.py", line 416, in majorminor
    sysfs_path = get_sysfs_path_by_name(device)
  File "/usr/lib/anaconda/storage/formats/lvmpv.py", line 153, in writeKS
    f.write("pv.%s" % self.majorminor)
  File "/usr/lib/anaconda/storage/devices.py", line 2751, in writeKS
    self.format.writeKS(f)
  File "/usr/lib/anaconda/storage/__init__.py", line 1188, in writeKS
    device.writeKS(f, preexisting=preexisting, noformat=noformat)
  File "/usr/lib/anaconda/instdata.py", line 289, in writeKS
    self.storage.writeKS(f)
  File "/usr/lib/anaconda/packages.py", line 66, in writeKSConfiguration
    anaconda.id.writeKS(fn)
  File "/usr/lib/anaconda/dispatch.py", line 208, in moveStep
    rc = stepFunc(self.anaconda)
  File "/usr/lib/anaconda/dispatch.py", line 126, in gotoNext
    self.moveStep()
  File "/usr/lib/anaconda/gui.py", line 1389, in nextClicked
    self.anaconda.dispatch.gotoNext()
  File "/usr/lib/anaconda/iw/progress_gui.py", line 79, in renderCallback
    self.intf.icw.nextClicked()
  File "/usr/lib/anaconda/gui.py", line 1410, in handleRenderCallback
    self.currentWindow.renderCallback()