Re: [gentoo-user] Correcting some misconceptions (was: What magic does portage use?)

[Bruce Hill]

On Wed, Dec 16, 2009 at 06:56:00PM -0600, Leslie Turriff wrote:
> 	As a 30-year veteran of the IBM mainframe programming environment, I can say
> with authority that most of the enterprises that use them for
> mission-critical business applications (banking, stock-brokerage, etc.) are
> running systems that are updated frequently (sometimes daily) and are fully
> capable of being shut down and restarted (on purpose :-D ).  Yes, some of
> them are front-ended with Linux servers; mainframe systems are not well
> designed for managing dynamic web traffic, although systems that do not have
> to support very high-volume workflows can do it themselves.  The last system
> that I worked on was only shut down and restarted twice per year, because 90%
> of maintenance could be done while it was running (just like Linux), and
> because it was not a business-critical system, it was only required to be
> available 99.95% of the time. :-)
>
> 	The banking and brokerage systems that I first referred to use a more robust
> configuration than we did, which is capable of providing services 100% of the
> time, much like a Linux cluster system does.  IBM calls the
> configuration "Parallel Sysplex." Here's an excerpt of their technical
> description, from
> <http://www-03.ibm.com/systems/z/advantages/pso/sysover.html>:
>
> 	'This "shared data" (as opposed to "shared nothing") approach enables
> workloads to be dynamically balanced across all servers in the Parallel
> Sysplex cluster. This approach allows critical business applications to take
> advantage of the aggregate capacity of multiple servers to help ensure
> maximum system throughput and performance during peak processing periods. In
> the event of a hardware or software outage, either planned or unplanned,
> workloads can be dynamically redirected to available servers thus providing
> near continuous application availability.
> 	Another significant and unique advantage of using Parallel Sysplex technology
> is the ability to perform hardware and software maintenance and installations
> in a nondisruptive manner. Through data sharing and dynamic workload
> management, servers can be dynamically removed from or added to the cluster
> allowing installation and maintenance activities to be performed while the
> remaining systems continue to process work. Furthermore, by adhering to IBM's
> software and hardware coexistence policy, software and/or hardware upgrades
> can be introduced one system at a time. This capability allows customers to
> roll changes through systems at a pace that makes sense for their business.
> The ability to perform rolling hardware and software maintenance in a
> nondisruptive manner allows business to implement critical business function
> and react to rapid growth without affecting customer availability.'
>
> 	Respectfully,
>
> Leslie

Leslie,

I appreciate you addressing the previous FUD in such a professional manner.
-- 
"Experience is a hard teacher because she gives the test first, the
lesson afterward. But properly learned, the lesson forever changes
the man."