On Monday, 08/16/2010 at 07:27 EDT, "Bauer, Bobby (NIH/CIT) [E]" <[email protected]> wrote: > We have been asked to make a zLinux server running under z/VM 100% > availability, except for POR (power on reset). We have 2 z/VM lpars, a test and > a production but as far as I know, z/VM doesn?t have a sysplex takeover > mechanism. > > I can move the server from one lpar to the other easy enough but that move > would disruptive in itself.
*Servers* are never 100% available. A server is a single point of failure, whether it is a partition, a virtual machine, or a PC. Things Happen. *Applications*, on the other hand, can be made as close to 100% as is technologically possible because they can be designed to cooperate at a higher level, across multiple servers. Therefore they can be designed to survive outage of a single server. Can they survive the loss of two servers? Only if there are more than two servers available. z/VM having a SYSPLEX mechanism won't help you since SYSPLEX is an *application* service - it does nothing to improve the availability of an MVS address space. [Yes, SYSPLEX is used by MVS subsystems, but they are just privileged applications in this context.] What IBM *has* announced in a Statement of Direction is that in the future z/VM will have the ability to move a running virtual machine from one LPAR to another. This improves the availability of the virtual machine dramatically for planned hw or z/VM outages, but it doesn't go to 100% since you can still have an unplanned outage (the network, the server, the LPAR, z/VM, or the guest). So, taken literally, the request cannot be achieved on any platform. I can't imagine why They give a rat's behind whether a server is up or down. Presumably They only care whether an *application* is available. Solving application availability by making it a server problem is an architectural error of the highest order. Making servers more available during planned outages helps to keep the *applications'* HA elements up and running. (Imagine if the International Space Station had only one coolant pump active at any one time.) Alan Altmark z/VM Development IBM Endicott
