Adam I am shocked that the telco around you don't have redundant UPS
Heck a large number of the cell towers we work with and around even have this Even N+1 cooling is in place But I agree - depending upon your needs what you lay out is / should be more than enough On Oct 9, 2010, at 9:01 PM, Adam Thompson wrote: > It’s perhaps overkill for many scenarios, but if you’re truly trying for > no-single-point-of-failure, buy UPSes from two different vendors, ideally > using two different technologies. I’ve seen matched pairs of UPSes knocked > out by the same power event, and more commonly I’ve seen matched sets of > batteries fail without warning. To clarify, there are power events that will > kill an APC SmartUPS whereas their BackUPS won’t even notice a problem; on > the other hand, the SmartUPS will protect a power supply against some failure > modes that a BackUPS cannot. And a full-online-conversion UPS, while ideal, > costs an arm and a leg. All three will tolerate different amounts of input > power phase mismatch (“Power Factor”). > > It’s nearly impossible to design truly “uninterruptible” power; anyone who’s > installed a mainframe can attest to this! You need capacitors on the circuit > board to smooth ripples (micro-events), ultracapacitors or batteries to prop > up the input power during sub-second (or even multi-second) outages, a > traditional UPS to provide interim power, a generator to cover long outages, > and a ground-zero-grade blast shelter to put it all in so it stays running in > case of global thermonuclear war… and even then, we still don’t have a > technology to work around the power outages anticipated when the heat death > of the universe occurs. > > Yes, I’m being silly, but my point is that there’s no point in trying to > design a “perfect” system. “Better than normal” is almost always what you’re > really reaching for. > Having CARP failover is level 1, dual power supplies is level 2, dual UPSes > is level 3, how far do you plan to take this? What if your ISP goes down – > are you also going to multi-home? Are the devices behind this firewall also > multiply-redundant? > > I don’t mean to suggest there’s no point in increasing reliability, but even > two UPSes is going far beyond the needs of most applications. > “Carrier-grade” doesn’t even mean having redundant UPSes… at least, none of > the telcos I work with in my region have redundant UPSes powering their phone > switches! > > Anyway, like I said – if you’re going to run >1 UPS, use *different* UPSes to > avoid hitting the identical problem at the identical time on all of them, > which has actually happened to me. > > -Adam > > > From: Hans Maes [mailto:[email protected]] > Sent: Saturday, October 09, 2010 10:02 > To: [email protected] > Subject: Re: [pfSense Support] Dual WAN + Firewall Redundancy + UPS > Redundancy (?) at entrance > > > On 10/08/2010 07:15 PM, Gerald A wrote: > > On Fri, Oct 8, 2010 at 4:55 PM, Andy Graybeal <[email protected]> > wrote: > I'll have 2 firewalls, and 2 UPS's one for each firewall. > > Each firewall will have: > 1. a hot swap raid array (only two HD's set to RAID 1, mirroring). > 2. two hot swap power supplies. > > Is one UPS per firewall agreeable? I don't know how to do it otherwise. I > can't imagine purchasing 4 UPS's, one for each power supply. Seems a little > overkill. I welcome any input. > > Plug one hotswap supply from each firewall into both of the UPS boxes you > have. That way, even if you have to service a UPS, you won't lose a firewall. > I wouldn't dedicate a UPS to > each firewall, because any UPS issue makes your bring down a box no matter > what. > > > True, but depending on your configuration, another way to hook this up is to > bypass the UPS for one of the power supplies on each firewall: > > FW1 - Power supply 1 -> UPS1 > FW1 - Power supply 2 -> straight to power grid > > FW2 - Power supply 1 -> UPS2 > FW2 - Power supply 2 -> straight to power grid > > This way, you would still be up and running if both UPS systems fail for some > reason. > I've seen it happen! eg short circuit in a system connected to both UPS > triggering both UPS to shutdown. > (Try explaining complete power failure to your boss when all lights are still > on in the entire building ;-) ) > > Agreed, during power grid failure, FW1 would go down if UPS1 fails, and FW2 > would go down if UPS2 fails, but you got CARP to fix that. > > Just my 2 cents. > > Regards, > > Hans > >
