lists at alteeve
Aug 2, 2012, 4:55 PM
Post #2 of 3
On 08/02/2012 06:28 PM, Yount, William D wrote:
> So I have been giving some thought to my fencing agent, as it seems a proper fencing solution is integral to any cluster. I only have access to basic Optiplex 990 and 960 desktops which is what I have built my cloud out of. I have been using the fence_pcmk agent but that doesn't seem to be a great solution. It can send shutdown and reboot commands to other nodes, but the nodes usually get hung-up in their shutdown scripts waiting for NFS shares to unmount or for VMs to turn off.
> One agent that seems to come up a lot is OpenIPMI. I have done some reading on it and I can't quite get an understanding of if this is a software solution that doesn't need any hardware implementation such as a special IPMI management board. Can anyone let me know if I need hardware that specifically supports IPMI?
To clarify; A fence agent is designed to talk to a specific target
device. So fence_ipmilan only works if the target machine has an IPMI
BMC (baseboard management controller). Now I don't know Dell hardware,
but most desktop-class equipment does not have IPMI on it. These IPMI
BMCs are almost like little mini computers; They pull their power from
the same system, they can read the sensors of the host, etc, but they
are independent. These IPMI BMC are not generic devices you can add to a
machine, they have to be designed for the host. So if you don't have
IPMI, you're likely not going to add one.
You are right; fencing is critical. Fence agents that rely on the target
responding properly are fundamentally flawed and unreliable. The whole
idea behind fencing is to put a node in an unknown state into a known
state. If you don't know a node's state, there is a very good chance you
won't be able to talk to it, or even if you can, as you've seen, it
isn't operating properly anymore.
The best option at this point would be to use a switched PDU, like the
APC AP7900 (or similar, higher port-count version). These are
effectively network-connected power bars with individual outlet control.
You have to choose the maker carefully, as not all switched PDUs have
agents (APC, Eaton and a couple others do, I think). This is your best
bet to add fencing to your desktop machines.
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