Experiences with Oracle for Linux on zSeries

20 Experiences with Oracle for Linux on zSeries

The topology of a network using IUCV is the same as that illustrated in Figure 2-2

on page 18 using CTC adapters.

We have found that Guest LAN is easier to manage and provides better

performance, so we recommend that you use the Guest LAN facilities of z/VM

Version 4.3 rather than point-to-point connections with IUCV.

Network Topology without z/VM

If you deploy a number of Linux machines in logical partitions, without the use of

z/VM, then each Linux machine will be a peer on the network with the other

operating systems running in other logical partitions. This is illustrated in

Figure 2-4. Note that unlike a virtual machine under z/VM where the network

adapter address (NIC) has the same address as other virtual machines, when

you deploy in a logical partition, the operating system must see the real device

address of the NIC. Each of the Linux machines in Figure 2-4 will use different

device numbers to access the OSA/Express adapter.

Figure 2-4 Peer Linux guests in logical partitions

2.1.5 Capacity planning

Deploying Linux on zSeries processors must be approached with the same

methodology as deploying any other operating system. Consolidating multiple NT

or Linux servers onto Linux for zSeries can be a great idea, and can save money.

However, if you are planning to consolidate servers that are doing existing

MVS01z/OS z/OS z/OSz/OS

Shared OSA/Express LAN

Linux Linux Linux

Chapter 2. How to deploy Oracle9i on Linux/390 21

workloads, then you must measure the utilization of the existing servers and also

do some calculations to ensure that the configuration of Linux on the zSeries

processor is appropriate. The ITSO Redpaper

Server consolidation with Linux for

zSeries,

REDP0222, covers many of the capacity planning issues.

Performance considerations for Linux on zSeries are discussed more completely

in Chapter 8., “Performance and scalability considerations” on page 131. This

section will only discuss the basic considerations.

Number of CPs

The speed and capacity of a z/800 or z/900 machine are well understood.

However, deploying Linux on these machines will probably share these

resources through the use of LPAR with other workloads and other operating

systems. It will be fairly rare to dedicate a complete zSeries machine to a single

copy of Linux, even though that is the norm in other platforms. Each of the small

servers that are being consolidated onto the zSeries processor has the entire

capacity of the server available for peak loads, but probably (hopefully?) runs at

an average utilization much less than 100%. On the zSeries machine, all

resources are shared, and hopefully the peak activity of each Linux machine will

not occur simultaneously. You must analyze each of these servers and calculate

the expected utilization and number of CPs required to provide the capacity

required.

There are tools available from IBM to assist in this process. For a detailed sizing

study using a tool called SIZE390, contact your IBM representative. This tool can

help analyze the utilization of the servers that will be consolidated onto the

zSeries machine.

LPAR weights

As discussed in “Deploying in a logical partition” on page 12, each logical

partition is assigned a

weight. Processor resources are given to the various

logical partitions in the ratio of the weights. Normally, we recommend that the

sum of the weights assigned to the logical partitions sum to 100 or 1000. If this is

done, then the weight can be directly understood to be the percentage of total

capacity of the zSeries processor that is given to the specific logical partition.

Capacity greater than this percentage can be delivered to a given logical

partition, but only if no other logical partition wants the resources. The weight,

expressed as a percentage is the

target capacity of the logical partition. If, for

example, you want the Linux machines to get 40% of the capacity of the zSeries

processor, then the sum of the LPAR weights for the Linux logical partition should

be 40% of the total weights for all logical partitions.