Prior to z/VM and Linux, the mainframe environment provided mostly legacy applications. Now the applications can use z/VM with Linux as a platform choice competing well with Microsoft .NET and AIX. Looking ahead, z/VM with Linux will be part of the e-government service architecture including portal and Web. Oracle, WAS, Domino, and a hybrid TAM/LDAP are all options being considered. Many agencies are interested in the consolidation capabilities DGTIC has demonstrated.
z/VM with Linux should be a carrier for front-end, Service-Oriented Architecture (SOA) services. DGTIC can provide the bridge for .NET to legacy services; that represents the most economical method of integrating all the platforms for SOA.
Many valuable lessons have been learned. When performing proof of concepts involving performance characteristics or comparisons with other platforms, it’s important to plan the mainframe activities. The mainframe invariably won’t compare favorably if you take one application and plunk it into the mainframe. The mainframe will compare favorably when you run multiple instances of Linux servers and applications or if you have I/O-intensive applications.
Acceptance of the Oracle Linux virtual machine servers on z/VM has grown faster than planned; more than 100 servers were implemented. Today there are close to 200 Linux Oracle database instances with nearly 50 in production.
This environment is supported by a comparatively small staff. Two z/VM systems programmers under my tutelage support all the LPARS, z/VM, and vendor software. Two Linux system administrators support more than 100 Linux servers, a ratio of 50:1 virtual servers to a person. Additional personnel are required from time to time for security tasks, VM networking, disk storage management, automation, and performance monitoring and capacity planning.
On the technical side, we learned that Linux virtual machines like to consume resources, especially memory. A key factor in providing good response time is to provide a large amount of core memory and to have enough DASD paging space. Try to manage the z/VM paging space to never exceed 40 percent occupancy. Core memory should be allocated as central and a percentage as expanded storage. DGTIC runs with a maximum of 2GB of expanded storage, which provides good results. Your organization should find the optimal sizes for your workloads.
When doing a proof of concept, be careful of comparisons with other platforms. The hardware and software on the mainframe are optimized toward multi-tasking, multi-programming and I/Os, so avoid running one instance of Linux in a proof of concept. Rather, running multiple Linux virtual machines with the chosen applications will showcase the mainframe in a favorable, yet realistic fashion. After all, if using z/VM, you’ll most likely be using it to run many instances, not one.
When benchmarking Linux virtual machines, it’s important to avoid a “drop in and go” method. Since the mainframe is an intensively shared environment, Linux storage sizes should be carefully calibrated so they’re doing a small amount or zero swapping under normal workload conditions. Using the same storage sizes from a non-shared Intel server as your Linux virtual machine size is invariably a mistake, so avoid doing that.
The DGTIC project was highly successful. Interest from the DGTIC clients is quite high and the organization is ready to meet the upcoming demand.
“The Province of Quebec without question established a standard of excellence over the past year,” says Michael Bliss, IBM’s System z Technical Sales Support. “IBM is proud to see an organization experience wins to this degree using our technology in combination with SHARE’s educational opportunities.”