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@xxxxxxxxxxxx <bergman@xxxxxxxxxxxx> wrote: >>> The pithy ruminations from Digimer <linux@xxxxxxxxxxx> on " >>> 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... Fabio -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
