[CentOS] {OT] Re: Installing IMA (Integrity Measurement Architecture) on CentOS 5.5

[Les Mikesell]

On 3/24/2011 2:07 PM, m.roth at 5-cent.us wrote:
>
>> Having said that, I have this troubling thought for last decade: What
>> exactly is high availability: is it 24/7 power on time? or is ti "when
>> needed". Please not it am not talking about the maybe arrogant  "on
>> demand" attitude of a human.
>
> Ok, h/a is not "fault tolerance", which is for 99.+% uptime (and you *pay*
> a lot for additional decimals there).

Most of the computation in percentages is like computing rates for 
insurance - balancing the penalty for missing your SLA against the cost 
of providing it.  But on the operations side you can only work in 
integer numbers of instances.  You know everything will break and if you 
can't be down long enough to replace it, you need a complete duplicate 
copy, and then you may need to duplicate that pair in another location. 
  If you aren't already working with grid/cluster systems you almost 
always more than double your cost to get even the slightest increase in 
expected availability.

>> What exactly is "production" use? (I know DEV, UAT, blah, bla,  tla
>> etc been there done that and I don't have the T shirt - nobody gave me
>> one)
>
> All services expected from a server at a given IP should be available up
> to or over 99% of the time, with no lost transactions, or transactions in
> an undefined state - that's h/a and production.

Not everything deals in transactions, though.  The recently popular 
distributed database versions that scale up are more about doing 
something reasonable in scenarios where you can't guarantee a 
transaction state (where 'reasonable' is defined by the application).

-- 
   Les Mikesell
    lesmikesell at gmail.com