IBM Power Systems: create an LPAR from the HMC

Creating Logical Partitions (LPARs) on IBM Power Systems is a fundamental task for system administrators looking to optimize resource utilization and…

Creating Logical Partitions (LPARs) on IBM Power Systems is a fundamental task for system administrators looking to optimize resource utilization and isolate workloads. This process involves allocating virtualized hardware resources such as CPUs, memory, and I/O adapters to a specific operating system instance. The Hardware Management Console (HMC) provides a centralized interface for managing Power Systems hardware, including the configuration and deployment of LPARs.

This article details the steps to create a new LPAR using the HMC graphical interface, focusing on common configurations for AIX, Linux, and IBM i operating environments. We will cover initial setup, resource allocation, virtual I/O configuration via a Virtual I/O Server (VIOS), and LPAR activation for initial operating system installation.

Pre-requisites and Planning

Before beginning LPAR creation, ensure the following are in place:

HMC Connectivity: Ensure your HMC is online and connected to the managed Power System. Confirm the HMC firmware version is compatible with your Power System firmware (e.g., HMC v10R2M1000 for Power10 systems with FW1030).
VIOS Configuration: At least one Virtual I/O Server (VIOS) LPAR should be running and fully configured on the managed system. This VIOS will provide virtual SCSI and Ethernet resources to the new LPAR. Note the VIOS LPAR ID and its virtual slot numbers available for mapping.
Resource Allocation Plan: Determine the required CPU, memory, and I/O resources for the new LPAR based on its intended workload.
- CPU: Dedicated or Shared (uncapped/capped, processing units). Minimum 0.1 processing units for shared, 1.0 for dedicated.
- Memory: Minimum, desired, and maximum memory. A good starting point for a small AIX LPAR is 2GB desired memory. For Linux, 1GB is often sufficient for minimal installs.
- I/O: Number of virtual SCSI adapters and virtual Ethernet adapters required. Identify the physical network bridges on the VIOS.
VLAN IDs: Know the VLAN IDs for network connectivity.
Storage Strategy: Decide whether to use Virtual SCSI (vSCSI) or N_Port ID Virtualization (NPIV) for storage. This guide primarily focuses on vSCSI.

Navigating the HMC and Initiating LPAR Creation

Access your HMC via a web browser (e.g., https://your_hmc_ip_address). Log in with appropriate credentials (e.g., hscroot).

On the HMC GUI, navigate to Resources > All Systems.
In the content pane, select the Power System where you want to create the LPAR.
In the "System Actions" menu (often three vertical dots or a "Actions" dropdown), select Partitions > Create Partition. Alternatively, you might see "Partitions" as a direct tab or sub-menu on the selected system.

This will launch the "Create Partition" wizard.

Step 1: General Properties and Operating System

The first screen prompts for basic LPAR identification and operating environment.

Partition Name: Enter a unique, descriptive name (e.g., app_server_dev_01). Maximum 20 characters.
Partition ID: This is typically automatically assigned by the HMC.
Operating System Environment: Select from:
- AIX/Linux: For AIX and Power-based Linux distributions (RHEL, SLES, Ubuntu).
- IBM i: For IBM i (formerly AS/400, iSeries).
- VIOS: Specifically for Virtual I/O Server LPARs. (Do not select for client LPARs).
- Service Partition: A special type for service functions.
Partition ID: Usually auto-assigned. Leave as default unless a specific ID is required.
Boot Mode: Select Normal for most installations. SMS is used for accessing boot menus for advanced installations or diagnostics.

Click Next.

Step 2: Processor Allocation

Configure the CPU resources for the LPAR.

Processor Compatibility Mode: Leave as Default unless specific hardware compatibility is required (e.g., migrating an LPAR from an older Power system).
Processor Mode:
- Shared: Recommended for most LPARs, allowing CPU resources to be pooled and shared dynamically.
  - Number of Virtual Processors: Minimum 1. Specifies the number of virtual CPUs presented to the OS. Typically 1-4 for most small LPARs.
  - Desired Processing Units: The initial allocation of physical processor time. A value of 0.5 means the LPAR gets 50% of one physical core's capacity. For shared uncapped, this can burst above the desired.
  - Minimum Processing Units: The guaranteed minimum physical processor time. Often set equal to Desired.
  - Maximum Processing Units: The maximum physical processor time the LPAR can consume. Set to match "Desired Virtual Processors" for a dedicated-like experience or higher for bursting.
  - Processor Sharing Mode: Uncapped (default, allows bursting above desired) or Capped (strictly adheres to maximum processing units).
- Dedicated: Provides exclusive physical cores to the LPAR. Use for high-performance, latency-sensitive workloads.
  - Number of Processors: Set the number of dedicated physical cores.
  - Allow Dedicated Processors to be Donated: (Optional) Allows the LPAR to donate idle CPU cycles back to the shared pool, if configured.

For a typical small AIX/Linux LPAR, shared mode with 1-2 virtual processors, 0.2-0.5 desired processing units (min/max often matching desired), and uncapped is a good starting point.

Click Next.

Step 3: Memory Allocation

Define the memory resources.

Memory Mode:
- Dedicated: Memory is exclusively allocated to this LPAR.
- Shared: (Requires Active Memory Sharing (AMS) to be enabled on the system and VIOS). Allows memory to be pooled and dynamically allocated. Complex to set up, often not needed for initial LPARs.
Minimum Memory: The lowest amount of memory the LPAR can operate with.
Desired Memory: The amount of memory allocated at LPAR activation.
Maximum Memory: The upper limit to which memory can be dynamically added to the LPAR (if supported by OS and firmware).

A common setup for a mid-sized LPAR would be Minimum: 2048 MB, Desired: 4096 MB, Maximum: 8192 MB, allowing for future expansion without reboots.

Click Next.

Step 4: Virtual I/O Adapter Configuration

This is a critical step where the LPAR's I/O resources are virtualized and mapped to a VIOS.

Virtual SCSI Adapters

Click Add Adapter > Virtual SCSI Adapter.

Client Adapter ID: Auto-assigned, but can be manually set. Note this ID; it will appear as vhostN on the VIOS.
Client Adapter Slot: Auto-assigned.
Virtual I/O Server Partition: Select the VIOS LPAR from the dropdown list (e.g., vios_01).
Server Adapter ID: Auto-assigned. This corresponds to the virtual server adapter on the VIOS (e.g., vhostX). If you have multiple VIOS LPARs, repeat this for redundancy.

For a single VIOS, you'll typically add one virtual SCSI adapter. For redundant storage, add another and point it to a second VIOS if available.

Virtual Ethernet Adapters

Click Add Adapter > Virtual Ethernet Adapter.

Adapter ID: Auto-assigned.
Slot: Auto-assigned.
VLAN ID: Enter the primary VLAN ID for the LPAR (e.g., 101).
Additional VLAN IDs: Add any other VLANs the LPAR needs to access via this adapter.
Trunk Adapter: Check this if this adapter will carry multiple VLANs (usually the case).
Virtual I/O Server Partition: Select the VIOS LPAR (e.g., vios_01).
IEEE 802.1Q compatible adapter: Usually checked.
Access external network: Check this.
Virtual I/O Server Host Ethernet Adapter (HEA) logical port / Shared Ethernet Adapter (SEA): Select the Shared Ethernet Adapter (SEA) that bridges to the physical network on your chosen VIOS. The format will be similar to SEA on entX. If you have multiple SEAs on the VIOS (e.g., for different physical networks), choose the correct one.

Repeat for additional virtual Ethernet adapters if the LPAR requires separate network interfaces for different purposes or VLANs (e.g., one for management, one for data, one for backup).

Click Next.

Step 5: Physical I/O and Console

Unless you are allocating dedicated physical I/O (e.g., a dedicated Fibre Channel adapter), you will typically bypass or confirm no physical I/O is added here. Most LPARs use virtualized I/O through VIOS.

Console Type: Select HMC Remote Virtual Terminal. This allows you to open a console window directly from the HMC to interact with the LPAR during boot and installation.

Click Next, then Finish to create the LPAR profile. The LPAR is now defined but not running.

Activating the LPAR for Installation

After creation, the LPAR appears in the HMC's partition list. To install an OS, you need to activate it, usually into SMS mode initially.

Navigate to Resources > All Systems, select your system, then Partitions.
Select your newly created LPAR.
From the "Partition Actions" menu, select Activate > Profile.
Ensure the correct profile is selected (usually Default, or the one you just created).
Under "Boot Mode," select SMS. This will allow you to access the System Management Services menu to select your boot device (e.g., network install or virtual optical drive).
Ensure Open a terminal window or console session is checked.
Click OK.

A console window will open, displaying the SMS menu or boot sequence. You can then configure network boot, choose a virtual optical device provided by the VIOS, or proceed with other installation methods.


# Example VIOS command to map a virtual SCSI adapter to storage
# Assuming you have created client LPAR with vSCSI client adapter ID 3
# and you have a hdisk2 and hdisk3 on your VIOS for redundancy

# List available disks on VIOS
lsdev -type disk

# Create a virtual target device (vtd) for LPAR client adapter 3 using hdisk2
mkvdev -vdev hdisk2 -vadapter vhost0 -dev client_lpar_vtd1
# Replace vhost0 with the actual server adapter ID for the client's vSCSI adapter

# For a second VIOS, mapping to client's adapter ID 4
# mkvdev -vdev hdisk3 -vadapter vhost1 -dev client_lpar_vtd2

# Example VIOS command to list virtual adapters and their mappings
lsmap -all -npiv

Common Pitfalls and Troubleshooting

Insufficient Resources: If the LPAR fails to activate, check the HMC logs (Manage Power System > View System Events) and ensure sufficient physical CPU and memory resources are available on the managed system.
VIOS Mismatch: Verify the selected VIOS and its virtual adapter IDs (vhostX) are correct. Mismatched or non-existent VIOS mappings will prevent the client LPAR from seeing storage or network.
Incorrect VLAN ID: A wrong VLAN ID on the virtual Ethernet adapter will prevent network connectivity. Double-check your network configuration.
SMS Mode Hang: If the LPAR hangs in SMS mode, ensure you have correctly configured a boot device (e.g., network boot server or virtual optical media via VIOS). Use the HMC console to navigate the SMS menus.
HMC Firmware/System Firmware Incompatibility: Ensure your HMC firmware is up-to-date and compatible with your Power System's firmware. Significant feature changes often require HMC updates.
Virtual SCSI Adapter ID vs. Server Adapter ID: Remember that on the client LPAR, you assign a "Client Adapter ID" (e.g., 3). On the VIOS, when you create the virtual target device (VTD), you specify the "Server Adapter ID" (e.g., vhost0) that corresponds to that client adapter. Ensure these match up.