Pros and Cons of Running Linux on zSeries Hardware

Given the ability of the zSeries platform to run various distributions of Linux, the question comes up - does it make sense to do it and under what circumstances. This paper will address two questions under this general category. What are the pros and cons of running under zLinux compared to zOS, and what are the pros and cons of running under zLinux compared to other Linux platforms.

Pros

Cost Savings
The biggest benefit of running on zLinux over the zOS platform is the significant cost savings both in hardware and software that you get from using the IFL engines over conventional engines.

Server consolidation
if you are in an environment where you want to have multiple servers but the server utilization is very bursty and random, you can consolidate all the servers under the z/VM operating system and you can let it manage the resource balancing across all the virtual servers.

Hipersockets
if you need high speed connectivity to the zOS operating system or to other zLinux LPARs, you can’t beat the cross memory bandwidth of hipersockets.

Cons

Hard to move traditional TSO Batch workload
Usually the apps that are best run on zLinux are what IBM terms “new workload”, for example Websphere Java, or C++ apps. If you are planning to run a more traditional batch workload, you’ll need to ensure that you have a job scheduler system that can schedule these jobs on Linux, e.g. Tivoli or CA Unicenter/Autosys.

CPU bound apps
If your application is extremely CPU intensive, you will find that even at a price much cheaper than conventional engines, IFLs are still an order of magnitude more expensive than Intel based CPUs. So if you are doing intensive number crunching or other CPU intensive work, you may want to consider the Intel platform. However, if your apps need mainframe data, you will still need to solve the problem of how to access it efficiently from the Intel platform. (See Corigin experience report for one way of doing this)

Pros
Cost Savings	The biggest benefit of running on zLinux over the zOS platform is the significant cost savings both in hardware and software that you get from using the IFL engines over conventional engines.
Server consolidation	if you are in an environment where you want to have multiple servers but the server utilization is very bursty and random, you can consolidate all the servers under the z/VM operating system and you can let it manage the resource balancing across all the virtual servers.
Hipersockets	if you need high speed connectivity to the zOS operating system or to other zLinux LPARs, you can’t beat the cross memory bandwidth of hipersockets.

Cons
Hard to move traditional TSO Batch workload	Usually the apps that are best run on zLinux are what IBM terms “new workload”, for example Websphere Java, or C++ apps. If you are planning to run a more traditional batch workload, you’ll need to ensure that you have a job scheduler system that can schedule these jobs on Linux, e.g. Tivoli or CA Unicenter/Autosys.
CPU bound apps	If your application is extremely CPU intensive, you will find that even at a price much cheaper than conventional engines, IFLs are still an order of magnitude more expensive than Intel based CPUs. So if you are doing intensive number crunching or other CPU intensive work, you may want to consider the Intel platform. However, if your apps need mainframe data, you will still need to solve the problem of how to access it efficiently from the Intel platform. (See Corigin experience report for one way of doing this)