Hi list, I'm new to clustering, and I'm running a little cluster@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) (id:order-drbd_ms-drbd0_fs-mandatory) promote drbd1_ms then start drbd1_fs (Mandatory) (id:order-drbd1_ms-drbd1_fs-mandatory) start drbd1_fs then start pgsql_res (Mandatory) (id:order-drbd1_fs-pgsql_res-mandatory) start drbd0_fs then start samba_res (Mandatory) (id:order-drbd0_fs-samba_res-mandatory) start samba_res then start nmbd_res (Mandatory) (id:order-samba_res-nmbd_res-mandatory) start drbd1_fs then start libvirt_res (Mandatory) (id:order-drbd1_fs-libvirt_res-mandatory) start libvirt_res then start libvirt_guest_res (Mandatory) (id:order-libvirt_res-libvirt_guest_res-mandatory) Colocation Constraints: drbd0_fs with drbd_ms (INFINITY) (with-rsc-role:Master) (id:colocation-drbd0_fs-drbd_ms-INFINITY) drbd1_fs with drbd1_ms (INFINITY) (with-rsc-role:Master) (id:colocation-drbd1_fs-drbd1_ms-INFINITY) drbd1_fs with pgsql_res (INFINITY) (id:colocation-drbd1_fs-pgsql_res-INFINITY) drbd0_fs with samba_res (INFINITY) (id:colocation-drbd0_fs-samba_res-INFINITY) samba_res with nmbd_res (INFINITY) (id:colocation-samba_res-nmbd_res-INFINITY) drbd1_fs with libvirt_res (INFINITY) (id:colocation-drbd1_fs-libvirt_res-INFINITY) libvirt_res with libvirt_guest_res (INFINITY) (id:colocation-libvirt_res-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 fencing?
Thanks in advance.
Alessandro.