Description of problem:
Currently it is not possible to use LVM on top of iSCSI devices. Basically, 
LVM initialization happens during disk initialization, which is right at the 
start of init. Where as the network and iSCSI (also multipath) services start 
way later. Hence, without iSCSI being started, LVM is not able to initialize 
the PVs because iscsid isn't started and no LUNs are mapped to the host.

There is a work around to this issue by manually re‑scanning the PVs after
the OS has completely booted. But this will be a problem if there are 
applications which are configured to use the LV as their data path because 
the applications will start automatically on system startup and will fail by 
not finding the Logical Volume/Mount Point.

Version-Release number of selected component (if applicable):
All

How reproducible:
Always

Steps to Reproduce:
1. Configure iSCSI and map some LUNs to the host
2. Create a VG/LV on top of those LUNs
3. Set them to auto-mount at boot.
4. Upon boot, the devices aren't mounted because the PV/VG aren't seen to the 
OS
  
Actual results:
Logical Volumes are not found because the LUN was not mapped at the time of 
LVM initialization which further leads to failure of mount points which are 
part of LVM

Expected results:
Device-Mapper should have the ability to do an LVM re-scan when it senses that 
a new block device has been plugged in.


Additional info:
This isn't specific to iSCSI. Can be reproducible with any block device 
providing application which starts-up in init after LVM initialization is 
done.