[CentOS] Question about clustering

Sun Jun 15 12:54:28 UTC 2014
Alessandro Baggi <alessandro.baggi at gmail.com>

Hi list,
I'm new to clustering, and I'm running a little cluster at home. The 
cluster is running on a  workstation hardware and running on Centos 6.5. 
Component: corosync, pacemaker, drbd and pcs. All works good.
This cluster has different resources:

1) drbd0
2) drbd1
3) drbd0_fs
4) drbd1_fs
5) pgsql
6) smb + nmb
7) libvirt (lbs)
8) libvirt_guests (lsb)

I've this constraint colocation and ordering constraint (sorry for format):

Ordering Constraints:
   promote drbd_ms then start drbd0_fs (Mandatory) 
   promote drbd1_ms then start drbd1_fs (Mandatory) 
   start drbd1_fs then start pgsql_res (Mandatory) 
   start drbd0_fs then start samba_res (Mandatory) 
   start samba_res then start nmbd_res (Mandatory) 
   start drbd1_fs then start libvirt_res (Mandatory) 
   start libvirt_res then start libvirt_guest_res (Mandatory) 
Colocation Constraints:
   drbd0_fs with drbd_ms (INFINITY) (with-rsc-role:Master) 
   drbd1_fs with drbd1_ms (INFINITY) (with-rsc-role:Master) 
   drbd1_fs with pgsql_res (INFINITY) 
   drbd0_fs with samba_res (INFINITY) 
   samba_res with nmbd_res (INFINITY) 
   drbd1_fs with libvirt_res (INFINITY) 
   libvirt_res with libvirt_guest_res (INFINITY) 

Today, starting my  "cluster", I've encontered a (obscure-not 
identified) problem during libvirt_guest_res start, and I've noticed 
that drbd1_fs was stopped because libvirt_guest_res has failed, and 
consequently all other resource that depend from drbd1_fs was stopped.

I suppose that this behaviour is colocation constraint related (correct 
me if I'm wrong).

In my case I've:

drbd1_fs with libvirt_res
libvirt_res with libvirt_guest_res
drbd1_fs with pgsql

There is a way to avoid that if libvirt_guest_res fails, drbd1_fs will 
not be stopped and then all other resources depending from drbd1_fs?

Another question is about fencing. I've ridden that a cluster must have 
fencing to be considered as such. On CentOS 6.5 there is stonith that 
concerns node level fencing. For this type of fencing I must have ilo, 
ilom, drac, and other. It's possible to have fencing without Light-out 
devices, blade power control device and other? There are other device 
that can be used for fencing? Supposing a 2 node cluster with two server 
assembled (no hp, dell, sun, ibm..) how I can implement fencing with 
stonith? I can run a cluster without fencing and what implies do not use 

Thanks in advance.