[Linux-cluster] Tripp Lite switched PDU fence agent; exists?

Fabio M. Di Nitto fdinitto at redhat.com
Fri Mar 18 18:29:32 UTC 2011

On 3/18/2011 5:29 PM, Digimer wrote:
> On 03/18/2011 06:36 AM, Rajagopal Swaminathan wrote:
>> Greetings,
>> On 3/17/11, bergman at merctech.com <bergman at merctech.com> wrote:
>>> The pithy ruminations from Digimer <linux at alteeve.com> on "[Linux-cluster]
>>> Tripp Lite switched PDU fence agent; exists?" were:
>>> Finally, I'd like to warn people away from using the TrippLite PDU model
>>> PDUMH15ATNET as a fencing device. While it seems to have nice features, it
>>> has
>>> a design choice that is a serious problem with fencing--when a command is
>>> given to power down an outlet, there is a "random" delay (observed to be
>>> about 17 to 35 seconds) before that command is executed. This has been
>>> acknowledged by TrippLite support as a design choice, with no option or
>>> setting
>>> to override this behavior.
>> This "powerfence" should come nowhere near a production cluster.
>> Such randomness can play havoc in the predictability of availability:
>> Just think two of those strips (A,B) used for each of the redundant
>> power inputs and they not being switched off together. can get _very_
>> messy.
>> Just my 2paise
>> Regards,
>> Rajagopal
> At the end of the day, I think the argument for or against a device's
> use should be secondary to it being supported. It's difficult to predict
> why a user may want to use a given piece of hardware. I'm hoping that
> adequate warnings in the docs to potential drawbacks will suffice.
> As for this specific device, I'd not seen a review of it when I ordered
> it. I plan to write an amateur review and I will specifically test for
> these issues. If I can not find a safe way around queued fence calls,
> then I will certainly include that in the review. That should hopefully
> help steer people away from using this device, should the delay be a
> show-stopper for them.

Wouldn´t it be possible for the agent to:

1) issue OFF command
2) either poll for OFF status or wait > $known_random_max_delay
3) issue ON command
4) profit?

even if it takes time to fence, it would make it usable.

Not all fence devices are millisecond fast either...


More information about the Linux-cluster mailing list