Chapter 4. IBM RS/6000 and IBM pSeries products 115
Following is an approximation of free space required in various filesystems
and volume groups:
The recommendation for rootvg is 2 GB, providing that /spdata is installed
in a separate volume group.
/var requires at least 20 MB of free space. Most of the PSSP logs are
stored here. The actual disk space used by these logs depends entirely on
the types of problems that occur on your system and their frequency. The
/var filesystem should be monitored frequently to ensure that there is
always sufficient free disk space for new logs.
/tmp requires at least 16 MB of free space.
We suggest that you create a separate file system for /tftpboot. Each
lppsource level requires a minimum of 25 MB. You should also consider
future AIX installations. We suggest 25 MB x (number of AIX versions+1).
For example, if you are installing AIX 4.2, 4.2.1, and 4.3, then you will
need 25 MB x (3+1) = 100 MB.
Downloading all of the AIX filesets to the lppsource directory requires
approximately 1.5 GB of disk space. Downloading only the minimal filesets
requires approximately 500 MB. Each mksysb image may vary between
100 MB and 700 MB. A simple example for AIX 4.3.2 is:
lppsource + mksysb_images + pssp_lpp_images + SPOT = total disk
lppssource = 500 MB
mksysb_images = 300 MB
pssp_lpp_images = 350 MB
SPOT = 200 MB
500 MB + 300 MB + 350 MB + 200 MB = 1.35 GB
You should have at least 1.35 GB of free disk space for the /spdata file
system. To be on the safe side, reserve 2 GB of disk space for /spdata. For
multiple AIX and PSSP version coexistence, this figure will increase
considerably due to the disk space taken up by different versions of
mksysb images, SPOT, AIX, and PSSP filesets.
4.2.6 Sizing and configuring an SP system
Since the initial introduction of the IBM RS/6000 SP systems, IBM has
continued to announce new node types with faster performance and better
price/performance ratios. Today, all the types of SP nodes are SMP nodes.
116 RS/6000 and IBM ^ pSeries Performance and Sizing Node selection
When selecting nodes for an SP system, we can use the methodology shown
in Figure 45 as a general rule.
Figure 45. Node type selection
* The 332 MHz PowerPC node is supported but a new POWER3 node is
1. Scientific/Technical Application
A scientific/technical application generally needs high floating-point
processor performance. The POWER3 chip has higher floating-point
processor performance than PowerPC 604e. The SPECfp_base_rate95 of
the POWER3 SMP 8way High Node is 1760, and that of the 332 MHz SMP
4way Wide/Thin Node is 364.
Also, if your application requires large memory, the high node is
recommended. Because the maximum memory size of the POWER3 SMP
High Node is 16 GB and that of the POWER3 Wide and Thin Node is 4
2. Commercial Application
If you use a commercial application, consider how much I/O is required.
The S80/S7A SP-Attached Node is recommended when very heavy I/O
332 MHz
How much
How much
High Nodes
Ye s
Start here
Chapter 4. IBM RS/6000 and IBM pSeries products 117
and very large scalability are required. If the I/O is heavy but not large
scale, you can chose POWER3 SMP Nodes. If the I/O is medium or light,
332 MHz SMP Wide Node is recommended. Commercial applications
generally need many PCI slots. Parallel sizing factors
Sizing a scalable system for commercial applications is different from sizing a
non-scalable system. It depends on the type of commercial applications, and
the following factors should be considered. Usually there are two types of
commercial applications predominately used on a scalable system; Decision
Support System (DSS) and On-line Transaction Processing (OLTP).
The performance metrics for the system designed for OLTP applications are:
Response time
N-node scale-up
The performance metrics for the system designed for DSS applications are:
Response time
N-node scale-up
N-node speed-up
Database scale-up
Scale-up and speed-up
In the case of scale-up, twice as much hardware capacity typically should
perform twice the work in the same elapsed time. Scaling up a scalable
system can be done in two ways, as shown in Figure 46 on page 118. The
first case occurs when increasing the data and resources equally. In this
case, perfect linear scaling will produce the same elapsed time. In the second
case, the amount of data increases while the resources stay constant. In the
latter case, elapsed time should increase proportionally to the workload

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