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

Digimer linux at alteeve.com
Fri Mar 18 16:29:16 UTC 2011

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.


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