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Re: Debian hotswap and 5 9's



John Griffiths said:

> Oh c'mon, iv'e got a frewall here running on an old HP pavillion 7400
> (PII200) it's downtime's well less than 5 minutes a year.

that hardly counts when someone thinks of "5 9s" i think. I have a
P200 that has more then 600 days uptime but I wouldn't trust it to
anything critical. both yours and my systems have probably a dozen
single points of failure, any of which will bring the system completely
down, many of which will cause severe damage and probable data loss.

Some systems, especially larger ones, a reboot can take more then 5
minutes, there goes the 5 9s right there, don't think about upgrading
the kernel or anything, better hope theres no security problems or that
you run a trusted system!

getting 600 days of uptime is a matter of luck mostly on systems
like ours. Also 5 9s would involve extensive power protection, backup
generators and other things(my former employer had two 3 hour power
outages in the space of 2 months this past summer, my biggest UPS
had 300 pounds of batteries on it, and it barely lasted 3 hours and
thats AFTER I shut down half the equipment connected to it to keep
the more critical stuff running). We didn't have the budget for
a generator.

> depends what it's being used for surely?

yes, I guess it too depends on perspective. Some people may think
they want 5 9s of uptime but in reality they don't care if they
are down for 5-10 hours accross a year's timeframe.

> (ok, and if soemthing DOES fail I'm down for a day)

which is funny, I read something recently, in theregister:

"When Microsoft goofed the DNS settings on its microsoft.com
servers recently, he figured the site would have to be up for
the next two hundred years to achieve five-nines uptime."

http://www.theregister.co.uk/content/53/28259.html

> having said that anyone who's todding "five 9's" around as a phrase
> probably wants to do something a bit more demanding.

either that or they don't know what they are talking about. my
previous company it seemed everything was "critical", but in reality,
it didn't matter if there was on the order of say 20-30 hours a year of
downtime on most servers. I mean, even our most critical servers
were down for more then 2 weeks while they were moved from washington
state to new hampshire on a truck. How many centuries to attempt to
regain 5 9s of uptime after that? :)

the places that I have worked at probably aim for 95% uptime to be
minimum. not sure how many hours or days a year of downtime that
calculates to ..


nate





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