RE: Bits from the RM

["Julian Mehnle" <lists@mehnle.net>]

cobaco <cobaco@linux.be> wrote:
> On 2003-08-20 15:33, John Goerzen wrote:
> > tne pain of breaking desktops is no less when
> > you consider how many more desktops we're talking about here.
> 
> that's assuming that all those desktops crash at the same time no?

No, it's assuming that all those desktops crash with the same average frequency (probability) per duration.

Consider one s = 1 company server serving c = 1000 clients (used by one user each).  Let's assume any one instance of a server software (e.g. Apache) crashes with a probability p_crash = 1% at any given time (i.e. it's down 1% of the time assuming a zero recovery time), and any one instance of a client software (e.g. Mozilla) does the same.  Now the expected number of users u_affected who can't use the company's intranet at any given time is...

...due to server failures:

  s * p_crash * u_aff,s = 1 * 0.01 * 1000 = 10

...due to client failures:

  c * p_crash * u_aff,c = 1000 * 0.01 * 1 = 10

(Of course, these sets of users do overlap, but that's not relevant here.)

So, assuming an equal crashing probability (AKA stability) of server and client software, "the pain of breaking desktops is no less" than the pain of breaking servers.  qed.