Bob Apthorpe wrote to [EMAIL PROTECTED]: > On Wed, 30 Jun 2004 18:10:23 -0600 (CST) Ryan Thompson <[EMAIL PROTECTED]> > wrote: > > Mike Hogsett wrote to SpamAssassin: > > > > In your case, I think it's more about efficient tuning than fault > > tolerance. Why exactly did spamd become ``wedged''? What do you mean > > by that? Did you exhaust some resource on the machine (VM, CPU, > > disk, sockets, etc?) [...] > > Optimizing your code and configuration buys you nothing if you burn a > network card, power supply, or disk.
Agreed, Bob. Recall that the OP mentioned spamd becoming "wedged", and not about failed hardware. I didn't want to get too far afield. > Don't mistake availability for efficiency. I'm not arguing against > optimization; it's just that it's the solution to a different problem. Efficiency *is* an important part of availability! Would you rather go do a department store that had one really fast cashier open, or three that each took ten minutes to ring through a single-item sale? If the cashiers are slow enough on a busy day, eventually the lineups will back up and crash the display of picture frames. And, many people will also likely give up and go away, which also indicates reduced availability. Say, also, that, on average, people, on average, give up after five minutes. Now it doesn't matter if you have a a hundred slow cashiers... although all of those queues are going to use a lot of resources (square footage, power, payroll, ...). Serving a request in half the time can do much, much more than double the throughput of a system. The point is, all sorts of funny things can happen, the longer it takes to serve an individual request. > > If you do have N > 1 server, you can add fault tolerance as you have > > with simple round-robin strategies. You probably won't get *much* > > better than that without spending a lot more money in HA clustering > > configurations, but you can have some significant gains by simply > > remembering that each machine is still critical to production. > > Administer each as if it were your only mail gateway. > > Round-robin DNS is poor man's loadbalancing. Right, and it works reasonably well in many applications. :-) (And it's also what the OP has already configured) The rest of the suggestions you make are quite good, to the general question of availability. > -- Bob > > [1] The classical definition of risk is the product of an event's > probability and its consqeuences. There are other exacerbating or > compensating factors, but the classical definition is suitable for this > case. It'd be a different story if the risk was people's kids being set > on fire. Yes, we're all utilitarians at heart. :-) - Ryan -- Ryan Thompson <[EMAIL PROTECTED]> SaskNow Technologies - http://www.sasknow.com 901-1st Avenue North - Saskatoon, SK - S7K 1Y4 Tel: 306-664-3600 Fax: 306-244-7037 Saskatoon Toll-Free: 877-727-5669 (877-SASKNOW) North America
