By Alan Swahn
Subcapacity licensing is just what it sounds like, software applications can be licensed for a portion of a server or group of servers and goes hand-in-hand with a variety of virtualization technologies and multi-core chips on the market. On the one hand, there is a lot of flexibility to fully utilize the underlying hardware and quickly provision or move partitions that contain the accompanying software applications between several networked servers. On the other hand, understanding the impact (software license liability) of virtual machine or hardware partition movement within the environment is somewhere between challenging and daunting. Challenging costs more than it should; daunting costs way too much.
As a simple example, let’s suppose you have a group of virtual servers that consists of:
|
IBM Server |
# Cores |
# PVUs per Core1 |
|---|---|---|
|
POWER5 QCM |
4 |
50 |
|
POWER6 520 |
2 |
80 |
|
POWER5 |
2 |
100 |
|
POWER6 570 |
2 |
120 |
|
POWER6 595 |
2 |
120 |
and a partition that is allocated 2 cores and contains 3 applications with an aggregate price of x dollars per Processor Value Unit (PVU). Since they are in the same partition on the same server, the application cost is:
2 cores * # PVUs per core * x
|
IBM Server |
# Cores Available |
# Cores used by VM |
# PVUs per Core |
# Cores * PVUs per Core |
App Cost |
Relative Cost |
|---|---|---|---|---|---|---|
|
POWER5 QCM |
4 |
2 |
50 |
100 |
100x |
1 |
|
POWER6 520 |
2 |
2 |
80 |
160 |
160x |
1.6 |
|
POWER5 |
2 |
2 |
100 |
200 |
200x |
2 |
|
POWER6 570 |
2 |
2 |
120 |
240 |
240x |
2.4 |
|
POWER6 595 |
2 |
2 |
120 |
240 |
240x |
2.4 |
If the workload is moved from the POWER5 QCM to the POWER6 570 the cost jumps 240%.
Let’s put in some real applications and associated costs:
|
Applications |
Price per 10 PVU |
Price per PVU |
|---|---|---|
|
IBM DB2 Advanced Enterprise Server Edition |
$4362 |
$43.60 |
|
IBM WebSphere Commerce Professional |
$1,1252 |
$112.50 |
|
IBM Cognos Business Intelligence Professional |
$3,5402 |
$354.00 |
|
Total: |
$510.10 |
|
IBM Server |
# Cores Available |
# Cores used by VM |
# PVUs per Core |
Cost = # Cores * PVUs per Core * Price per PVU |
Relative Cost |
|---|---|---|---|---|---|
|
POWER5 QCM |
4 |
2 |
50 |
$51,010 |
1 |
|
POWER6 520 |
2 |
2 |
80 |
$81,616 |
1.6 |
|
POWER5 |
2 |
2 |
100 |
$102,020 |
2 |
|
POWER6 570 |
2 |
2 |
120 |
$122,424 |
2.4 |
|
POWER6 595 |
2 |
2 |
120 |
$122,424 |
2.4 |
Therefore, the price swing for running these applications is from $51,010 to $122,424. It’s easy to move workloads between virtual servers using technologies such as IBM’s Live Partition Mobility, just make sure the financial liability is understood or you could get an unbudgeted surprise! What’s really needed is a software license management solution that provides “what-if” analysis to tell you the financial impact of moving or provisioning workloads before changes are made. Unfortunately, IBM’s ILMT3 tool only reports on PVU based inventory, after the fact.
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