Advices for creating a new cluster

[digrouz]

Hello,

I'm new to proxmox and I'm amazed by the product!

I'm planning to configure a small proxmox cluster composed of 2 nodes (HP) with internal storage only to provide some proximity services to users. Is there anything to take into account ? any advice?

I already did:
- the basic setup of the cluster (https://pve.proxmox.com/wiki/Cluster_Manager#_create_the_cluster)
- configure the watchdog (https://pve.proxmox.com/wiki/High_Availability_Cluster_4.x#HP_ILO_.28module_.22hpwdt.22_.29)

Stupid question first, what is actually doing the watchdog ? is it a kind of fencing service ?

I understood from other posts in the forum than a two node cluster (as available in plain corosync) is not supported, what would be your advice for that ? I may consider adding a third small node that I have in spare, but if there is a way to avoid it, I would like to try it first.

Kind regards

 

[Klaus Steinberger]

for a working cluster you will need at least 3 nodes (or in the future an quorom node which of course does not run on the same machines)

Alternatively you can migrate live from one node to the other if you use ZFS in the storage, but currently not in the GUI

The watchdog is a kind of fencing device, HP ILO should be able to do that.

One way to get a third node (you really want to have a third one): Install proxmox on another machine which is stable enough, but it doesn't need to run VM's just use it for quorum (I used that during migration of some older Redhat Clusterand ESX Cluster to Proxmox, until i could empty all old servers)

 

[digrouz]

Thanks for your reply.

I have a hp microserver available that could do the third node.

I'm using ZFS as storage . Can you point me where to find the command to live migrate ?

Regarding the watchdog, is there any futher configuration ? I remember when I was doing RHClusterSuite configuration, the fence was requiring a user with specific rights on the ilo card, is it the case with the watchdog too ?

 

[dietmar]

A two node cluster is perfectly fine if you do not need/run HA. You also do NOT need a watchdog. Those things are only required for HA (High Availability systems).

 

[Klaus Steinberger]

No the the Watchdog works via IPMI

you have to load ipmi drivers
docu is here: https://pve.proxmox.com/wiki/High_Availability (search for fences)

for an IPMI watchdog do the following on each node:

apt-get install ipmitool (should also require anything else you need)

create /etc/modprobe.d/ipmi_watchdog.conf:

options ipmi_watchdog action=power_cycle panic_wdt_timeout=10

and in /etc/default/pve-ha-manager:

# select watchdog module (default is softdog)
WATCHDOG_MODULE=ipmi_watchdog

Not sure if ILO works same way (I have FTS Servers) but probably should do it

you can see if your watchdog runs with:

root@xxx# ipmitool mc watchdog get
Watchdog Timer Use: SMS/OS (0x44)
Watchdog Timer Is: Started/Running
Watchdog Timer Actions: Power Cycle (0x03)
Pre-timeout interval: 0 seconds
Timer Expiration Flags: 0x10
Initial Countdown: 10 sec
Present Countdown: 9 sec


Docu for replication: https://pve.proxmox.com/pve-docs/chapter-pvesr.html

 

[digrouz]

A two node cluster is perfectly fine if you do not need/run HA. You also do NOT need a watchdog. Those things are only required for HA (High Availability systems).

Is there any restriction outside HA ?
I mean let's imagine, I have a broken in my 2 nodes cluster, Can I still create new/stop/start VM's on the remaining node ?

 

[dietmar]

Is there any restriction outside HA ?
I mean let's imagine, I have a broken in my 2 nodes cluster, Can I still create new/stop/start VM's on the remaining node ?

You need to make sure you have quorum. If you have only a single node, and the other nodes is known to be down, you can re-gain quorum by setting expected votes to 1

# pvecm expected 1

 

[digrouz]

You need to make sure you have quorum. If you have only a single node, and the other nodes is known to be down, you can re-gain quorum by setting expected votes to 1

# pvecm expected 1

ok thanks for the advices