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RE: availability and resiliency
- From: Roeland M.J. Meyer
- Date: Fri Sep 29 14:34:58 2000
Title: RE: availability and resiliency
It
refers to the percent uptime of a host or site. 99% is two "9"'s (2x9?) and
99.9% is three nines. Getting a single host to meet more than three nines
(99.9%) can be a challenge ( <8.76 hours outage, per year), but can be more
easily met with multiple hosts in a site. Four nines (99.99% uptime, <0.88
hours annual downtime) is extremely difficult for a single host, less difficult
for internal data centers, and (given lots of $$$) a bit easier for a internet
site (using multiply redundant hosts). Five nines (99.999%, <5.26 annual
minutes down) is almost impossible for a single affordable host to meet. This is
where we enter the world of High-Availability (H-A) systems. These are usually
high transaction flow critical systems and are found in large corps, telcos, and
reliable internet sites. At this time, only governments are willing to part with
the required cash to build systems meeting six nines (99.9999%, <0.53 minutes
annual downtime), or better (NASA, NORAD, US Space Command, etc). Usually, this
is done using multiple site redundancy.
Hosts
meeting three nines, or better, typically have redundant power supplies and
integrated UPS, bootable RAID for the OS, redundant NICs, and SMP CPU
configurations.
Pardon my ignorance, but what the heck does a "9" refer too?
Is it a UPS, rack, floor space, circuit...
Thanks in advance
-leo
-----Original Message-----
From:
Lionel Lauer [mailto:longword@newsguy.com]
Sent: Friday, September 29, 2000 10:54 AM
To: Andrew Bangs
Cc: nanog@merit.edu
Subject: Re: availability and resiliency
On Fri, 29 Sep 2000 17:39:04 +0100, Andrew Bangs
<andrewb@demon.net>
wrote:
>
>On Thu, Sep 28, 2000 at
02:39:40PM -0600, Irwin Lazar wrote:
>> Hi
all,
>> Does anyone know if a template exists
for what it takes to provide 5 9's of
>>
availability, 4 9's etc.for Internet data centers? Specifically I'm
looking
>> for something that would say "if you
want 5 9's of availability, here's what
>> you
need to do", and so on.
>
>For 5 9s you need:
>
>1) Lots of money
>2) Lots of clue
>3) Lots of luck
>4) Lots of
balls
>
>You can do 4 9s
with any 3 of the above.
Too true.
But you forgot to include 'halfway-clued management' - without
that you
haven't got a hope in hell of even getting
three 9's. ;)
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to
kill them." Perna condita delenda est
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