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."
