What is logical partitioning?

Logical partitioning (LPAR) is the ability to logically slice up a single system's CPU, memory, and other resources to create multiple and separate servers. Each LPAR has its own allocation of CPU, memory, and I/O devices. This type of partitioning is done at the firmware level, not at the physical resource level. Thus, with the IBM System p5 servers, you are able to create LPARs using Micro-Partitioning™ -- assigning less than one physical CPU per LPAR.

Figure 1 illustrates how the stand-alone server has only one operating system that can access the server's hardware.

On the other hand, the System p5 server (representation shown in Figure 2) can have multiple operating systems accessing the physical system's hardware. This is a very simple representation of what can actually be configured on a managed system.

Each LPAR contains its own operating system, which can be AIX®, Linux®, or i5/OS®. On a p5 system, you may only have one Linux or i5/OS partition.

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A special kind of LPAR: Virtual I/O Server

There is also a special kind of partition called a Virtual I/O Server (VIO Server). The VIO Server provides the ability to share I/O resources among several LPARs. You define virtual Ethernet and disk devices on the VIO Server and then make them available to the other LPARs on the system. Without the ability to share I/O devices on the managed system, each LPAR would require its own dedicated devices. If you have two LPARs on a system, you would need at least two Ethernet cards and two disk controllers. However, if you have 15 LPARs, then you would need at least 15 Ethernet cards and 15 disk controllers. With the use of VIO LPARs, you could host 15 LPARs with a much smaller number of Ethernet and disk controllers.

Of course, you are still able to dedicate I/O devices to an AIX partition if you need to for performance reasons. For example, if you have a large database LPAR that requires a large amount of throughput, you can dedicate a disk controller to that LPAR so that it won't have to compete for I/O resources with other LPARs using the VIO's disk controller.

On the other hand, you might have several small LPARs that do not require a large amount of data throughput. They would be ideal candidates for using the VIO Server since each of them would not completely utilize the full capacity of an Ethernet card or disk controller (see Figure 3). Together they could take full advantage of the hardware's capacity.

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Additional hardware needed

In addition to the System p5 server hardware, you need a Hardware Management Console (HMC) or the Integrated Virtualization Manager (IVM) to manage the LPAR environment. The HMC is a PC running a customized version of Linux that IBM has locked down so that the customer does not have root access, but it can only run the management applications provided by IBM. The IVM is available for entry-level servers where the added cost of an HMC would not make sense. The IVM does not provide the full functionality of an HMC. This article assumes the use of an HMC throughout.

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Dynamic logical partitoning

Not only are you able to logically carve up your hardware into multiple LPARs, but IBM provides the capability of dynamically adding, removing, or moving resources between the partitions while they are up and running. You can add or remove CPU, memory, or I/O slots to a running partition without first shutting that LPAR down. Dynamic logical partitioning (DLPAR) provides a great deal of flexibility to your computing environment. As conditions change in your environment, you are able to react by moving hardware resources to where they are needed without interrupting services to the LPARs. The options for using this feature are endless. A word of caution, though, not all applications are able to handle the removal of CPUs or memory gracefully, so testing is needed in your particular situation before you begin to use this feature in a production environment.

In the rest of this article, I'll discuss the steps you need to follow to configure an installed p5 system. It is impossible, in an article of this length, to discuss all the options available to you in configuring an LPAR system. Throughout the article, I'll cover the configuration basics and then point you to documents that provide more detailed information for that particular component. I'm also assuming the hardware is installed and connected to your network.

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Preliminary considerations

A great deal of planning is required before you order and purchase your System p5 server. Check out the IBM planning tools and documents (see Resources).

Before configuring LPARs on your System p5 server, you must first install and configure your HMC. Please refer to the IBM Hardware Management Console Best Practices document (see Resources) for installing and configuring your HMC.

You must also enable the Advanced POWER Virtualization feature before you can configure LPARs on your system.

1. On the HMC, open the Server and Partition folder and then the Server Management folder.
2. Right-click on the managed system you want to enter the validation code for.
3. Select Manage On Demand Activations > Virtualization Engine Technologies > Enter Activation Code.
4. Enter the activation code given to you by IBM to enable the virtualization feature.

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Creating the VIO Server

In order to partition a System p5 server, VIO servers are not required. However, if you plan on sharing Ethernet or disk hardware among your LPARs, you must first create a VIO Server. Without a VIO Server, each partition is required to have dedicated I/O devices.

Partitions and profiles

Each partition must have at least one profile. A profile describes the configuration for the partition. A partition might have more than one profile, each profile having a different resource configuration. For example, a particular application is heavily utilized during processing at the end of the month. You could have a profile named Month_End that is used to activate the partition just prior to processing at the end of the month that allocates a large amount of memory and CPU to the partition. When the processing at the end of the month is complete, you could then activate the partition using a profile named Non_Month_End that allocates a small amount of memory and CPU.

Creating the VIO server partition and profile

Before installing the VIO Server code, you must create a VIO Server LPAR and partition profile on the HMC. The VIO Server requires a minimum of 16GB of disk space and 512MB of RAM. Refer to the Virtual I/O Server Performance and Sizing Considerations document (see Resources)for help on determining how much CPU, memory, and disk space you want to allocate to this partition. The steps below walk you through creating a partition and profile for the VIO Server.

1. On the HMC, open the Server and Partition folder and then the Server Management folder.
2. Right-click on the managed system you want to create the partition on, select Create, and then Logical Partition.
3. Provide a name for your VIO Server, select the Virtual I/O ServeM radio button in the Partition Environment box, and click Next (see Figure 4).
   
   
   Figure 4. Create Logical Partition Wizard
   
   
   
4. If you are using workload management on this system, decide if this server will be included in a management group. If so, assign it to that group and click Next.
5. Enter a profile name for your partition and make sure the Use all the resources in the system check box is unchecked, as shown in Figure 5. Click Next.
   
   
   Figure 5. Create Logical Partition Profile
   
   
   
6. Enter the amount of memory you determine is appropriate for your system (see Figure 6). It is a good idea to have the maximum amount greater than the minimum or desired amount so that you can dynamically add memory later if necessary. However, if you make it too large, you can waste valuable memory resources on your managed system due to the size of the page table created for the partition. Table 1 (in Figure 7) shows the size of the page table space allocated based on the maximum partition memory value.
   
   
   Figure 6. Specifying memory for your system
   
   
   
   
   
   Figure 7. Page Table Space
   
   
   
7. Select Shared to assign processing units to the LPAR from the shared processing pool (see Figure 8). Select Dedicated to dedicate whole processors to the LPAR. Most people select Shared on the CPU panel so that they can take advantage of Micro-Partitioning. However, you have the option of selecting Dedicated, if your situation requires it. The instructions below assume you selected Shared.
   
   
   Figure 8. Assigning processing units to the LPAR
   
   
   
8. Enter the amount of minimum, desired, and maximum processing units (CPU) (see Figure 9).
   
   1. Minimum processing units: The number of processing units that must be available on the system when you activate this profile. If the processing units are not available on the system, then the LPAR will not start up. In addition, you will not be able to remove processing units from the LPAR below this amount.
   2. Desired processing units: The number of processing units that will be committed to the LPAR upon activation, if available on the system.
   3. Maximum processing units: The maximum number of processing units that can be dynamically committed to the LPAR.
      
      
      Figure 9. Entering the number of processing units
      
      
      
9. Select the Advanced button. There are two sections on this panel:
   
   1. Sharing modes -- Capped or Uncapped. Capped prohibits the LPAR from using more processing units than is currently allocated to it. If an LPAR is allocated 1.5 processing units but the workload requires 2.2 units, the LPAR would not be allowed access to the additional units, even if they were available in the shared processor pool. Uncapped allows the LPAR to use more processing units than is currently allocated. In this example, the LPAR would have access to the additional 0.7 processing units needed for the workload. If Uncapped is selected, you need to provide the Weight value for this LPAR. LPARs with higher Weight values receive higher priority when shared pool resources are fully used.
   2. Virtual processors tell the LPAR's OS how many physical processors it has. The OS cannot use parts of a processor, so you have to tell it in whole numbers how many processors it can use. Also, the number of virtual processors limits how many physical processors an LPAR can use. For example, if you give an LPAR two virtual processors, it cannot use more than two physical processors even though Maximum processing units is higher than two.
      
      • Minimum number of virtual processors: You must have at least one virtual processor for every part of a physical processor assigned to the LPAR. For example, if you have assigned 2.5 processing units to the LPAR, the minimum number of virtual processors is three.
      • Desired number of virtual processors: You can assign a virtual processor to every 0.1 processing unit allocated to the LPAR. There is no recommended value for this configuration setting. You need to use trial and error to determine what is the best setting for your application(s).
      • Maximum number of virtual processors: You can only have 10 virtual processors per processing unit. Therefore, you cannot assign a value greater than 10 times the maximum processing units value.
   3. Select OK and then Next (see Figure 10).
      
      
      Figure 10. Advanced Processing Settings
      
      
      
10. The I/O devices installed on your system are now presented to you.
    
    1. For the VIO Server, you must allocate at least one storage controller and one Ethernet card.
    2. When allocating I/O devices, a device can be present in more than one profile, but it can only be allocated to one partition at a time.
    3. To assign a device to the profile, you highlight the device and then click on Add as required or Add as desired.
       
       • Add as required: Use this option if this device must be present in order for the partition to function. If the device is allocated to another partition when this partition is activated, the partition will not start.
       • Add as desired: Use this option if this device is not critical to the functioning of the partition. If the device is allocated to another partition when this partition is activated, the partition will start.
    4. Click Next after adding all the I/O devices needed for this partition (see Figure 11).
       
       
       Figure 11. Adding I/O devices
       
       
       
11. The I/O Pool's panel is used for i5/OS, so ignore this for VIO Servers, AIX, and Linux partitions. Click Next.
12. Select Yes, I want to specify virtual I/O adapters and click Next.
13. You can now create virtual I/O devices that can be used by this and other partitions on the system. You'll notice that there are already two virtual serial devices created automatically (see Figure 12).
    
    
    Figure 12. Creating virtual I/O devices
    
    
    
    
    1. If you are going to share disk resources in the VIO Server with other LPARs, you will create virtual SCSI adapters. However, I will include the steps for that when you are configuring the AIX partition.
    2. Click the Ethernet tab.
    3. Click Create adapter (see Figure 13).
       
       
       Figure 13. Creating virtual SCSI adapters
       
       
       
    4. Select Access external network and IEEE 802.1Q compatible adapter and, for now, accept the defaults provided. Click OK (see Figure 14).
       
       
       Figure 14. Settings for the Virtual Ethernet adapter
       
       
       
    5. Click Create adapter.
    6. Select IEEE 802.1Q compatible adapter and click OK.
    7. Mark the Required check boxes for both Virtual Ethernet adapters (see Figure 15).
    8. The default value for Maximum virtual adapters is 10. Unless you have a small managed system or do not plan on utilizing the VIO Server extensively, this is too small. Increase it to a higher value based on your plans for your system.
    9. Click Next.
       
       
       Figure 15. Setting values for the Virtual Ethernet adapters
       
       
       
14. Power Controlling Partitions is only used for eServer™ i5 systems, so click Next.
15. See Figure 16 for optional settings .
    
    1. Enable connection monitoring: If selected, it enables monitoring of the connection between the HMC and the partition.
    2. Automatically start with managed system: If selected, this partition will automatically be activated when the managed system is powered on.
    3. Enable redundant error path reporting: If selected, server common hardware errors will be reported through this LPAR to the HMC, in addition to the path already in place from the service processor.
    4. Boot modes: Sets the default boot mode. This can be overridden at LPAR activation, so accept the default of Normal.
    5. Click Next.
       
       
       Figure 16. Optional settings for partition profile
       
       
       
    6. Review the Profile Summary and click Finish (see Figure 17).
       
       
       Figure 17. Profile summary
       
       
       

Installing the VIO Server using the HMC

Before installing the VIO Server code, you need to know the network configuration data for the server.

1. Insert the VIO Server CD or DVD into the HMC's DVD drive.
2. Enter installios on the HMC's command line to invoke the installios wizard where you can install the VIO Server code by answering the prompts.
3. Alternatively, the command in Listing 1 will install the code without the wizard prompts. The -n option tells the installation not to configure the network interface. You will do that manually.
   
   
   Listing 1. Command to install the VIO Server code without wizard prompts
   

   installios -p partition_name -i ipaddress -S subnet_mask -g gateway -d /dev/cdrom -s managed_system_name -m mac_address -r profile_name -n -P network_communication_speed -D duplex_value

   
   
4. When the installation is complete, open a terminal window to the partition on the HMC.
5. Log in as padmin and choose a new password.
6. Before using the VIO Server, you must accept the license.
7. To view the license, enter license -ls at the command line.
8. To accept the license, enter license -accept.

Configuring the VIO Server's network interface

In order to share the VIO Server's network interface with other LPARs, you will not configure the physical network adapter. Earlier, you created two Virtual Ethernet adapters in the VIO Server's profile. Because of this, there are now three Ethernet devices in your LPAR:

• ent0 is the physical adapter.
• ent1 is the first virtual adapter (marked Access external network).
• ent2 is the second virtual adapter (not marked Access external network).

Create a Shared Ethernet Adapter (SEA) that allows the VIO Server to access the network while also allowing other LPARs to use its physical adapter to access the network (see Listing 2).

                
mkvdev -sea ent0 -vadapter ent1 -default ent1 -defaultid 1

Configure the second virtual adapter with its network configuration settings. It uses the physical network adapter using the SEA just created to access the public network (see Listing 3).

                
mktcpip -hostname vio_lpar_hostname 
-inetaddr ipaddress 
-interface en2 
-netmask subnet_mask 
-gateway gateway 
-nsrvaddr dns_name_server 
-nsrvdomain dns_domain

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Creating an AIX partition

You will now create an AIX partition that uses the VIO server's SEA to access the network. It also has its rootvg hosted on the VIO LPAR.

Creating the AIX server partition and profile

Creating an AIX partition and profile is identical to the steps in the Creating the VIO server partition and profile section, except for the following changes.

1. In Step 3, select AIX or Linux instead of Virtual I/O Server in the Partition environment section (see Figure 18).
   
   
   Figure 18. Create Logical Partition Wizard for AIX
   
   
   
2. In Step 10, select only the storage bus that your CD/DVD device is connected to and click Next (see Figure 19).
   
   
   Figure 19. Selecting I/O components for partition profile
   
   
   
3. In Step 13, only create one Virtual Ethernet adapter and do not select Access external network. Make sure it uses Virtual LAN ID 1 (see Figure 20).
   
   
   Figure 20. Creating one virtual ethernet adapter
   
   
   
4. Select the Required check box (see Figure 21).
   
   
   Figure 21. Selecting the Required check box
   
   
   

Adding virtual SCSI devices to the VIO partition and profile

Currently, there are no virtual disk devices available to your AIX partition. You must configure these now on the VIO server partition profile.

1. Open the VIO partition's profile on the HMC (see Figure 22).
   
   
   Figure 22. VIO partition's profile
   
   
   
2. Open the Virtual I/O Adapters tab (see Figure 23).
   
   
   Figure 23. Virtual I/O Adapters tab
   
   
   
3. Click Create server adapter.
4. Select Only selected client partition can connect in the Slot connection settings area.
5. Select the Client partition you just created and enter 3 in the Client partition slot field.
6. Make note of the Server slot number assigned to this adapter (4) and click OK (see Figure 24).
   
   
   Figure 24. Noting the server slot number assigned to adapter
   
   
   
7. Click OK.
8. Right-click on the VIO Server partition (not the profile). Select Dynamic Logical Partitioning > Virtual Adapter Resources > Add/Remove and then repeat steps 3 through 6.

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Configuring virtual SCSI devices in the VIO server

You've created the virtual SCSI devices in the partition's profile. Now you must configure those devices within the VIO Server.

1. Log in to the VIO Server using Telnet or an HMC terminal window.
2. Enter cfgdev so that the VIO Server can see the new virtual SCSI device.
3. Create a volume group and logical volume to hold the client's rootvg. It is assumed that there is more than one disk attached to the disk controller allocated to the VIO Server (see Listing 4).
   
   
   Listing 4. Creating a volume group and logical volume
   

   mkvg -vg rootvg_clients hdisk1 mklv -lv rvg_client_name rootvg_clients 8G

   
   
4. Determine the vhost id of the virtual SCSI device (see Listing 5).
   
   
   Listing 5. Determining the vhost id of the virtual SCSI device
   

   > lsmap -all SVSA Physloc Client Partition ID --------------- ------------------------------------- ------------------ vhost0 U9117.570.1234567-V1-C3 0x00000007 VTD NO VIRTUAL TARGET DEVICE FOUND

   
   
5. Create the virtual target device that maps the virtual SCSI device to the logical volume (see Listing 6).
   
   
   Listing 6. Creating the virtual target device
   

   mkvdev -vdev rvg_client_name -vadapter vhost0 -dev vclientrvg

   
   

Adding virtual SCSI devices to the AIX partition and profile

Now that you have virtual devices defined in the VIO Server, you are ready now to define them for the AIX partition.

1. Open the AIX partition's profile on the HMC (see Figure 25).
   
   
   Figure 25. AIX partition's profile on the HMC
   
   
   
2. Open the Virtual I/O Adapters tab (see Figure 26).
   
   
   Figure 26. Virtual I/O Adapters tab
   
   
   
3. Click Create client adapter.
4. Select the VIO Server in the Server partition drop-down box.
5. Enter 4 in the Server partition slot field.
6. Click OK (see Figure 27).
   
   
   Figure 27. Client Adapter properties
   
   
   
7. Mark the adapter Required (see Figure 28).
   
   
   Figure 28. Marking the adapter Required
   
   
   
8. Click OK.

Installing the AIX operating system on the LPAR

You are now ready to install the AIX operating system into your logical partition.

1. Insert the first CD of the AIX 5L installation media. You must use Version 5.3 or higher to take advantage of Micro-Partitioning.
2. Right-click on the partition and select Activate (see Figure 29).
   
   
   Figure 29. Activate Logical Partition
   
   
   
3. Click on Advanced.
4. Select SMS in the Boot mode section and click OK (see Figure 30).
   
   
   Figure 30. Advanced activation settings
   
   
   
5. Select Open a terminal window or console session (see Figure 31).
   
   
   Figure 31. Activate Logical Partition
   
   
   
6. Click OK and a terminal window opens.

From this point, it is a normal AIX installation. The SMS and install menus are identical to those of a stand-alone server.

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Conclusion

Due to the nature of this article, I have only been able to cover just the basics of how to partition an IBM System p5 server. There are endless possibilities on how you could configure your managed system. For instance, it is advisable, for the sake of redundancy and availability, to have at least two VIO Servers per managed frame. Each of your AIX LPARs would then have one rootvg disk in each of the VIO Servers to provide mirroring of your rootvg volume group. Also, each AIX LPAR would have a SEA in each of the VIO Servers. Thus, if one of the VIO Servers were down, the client LPARs would still have network access and a rootvg volume through your second VIO Server. This is just one of many possible configurations of a System p5 server.

Hopefully, I have been able to show you that the IBM System p5 servers have the capability of consolidating multiple stand-alone servers onto one piece of hardware. By doing so, you are able to more fully utilize valuable hardware resources and free up expensive data center floor space.

Resources

Learn

• IBM Systems Hardware Information Center: Check out planning tools and documents from IBM.
  
  
• Virtual I/O Server: Performance and sizing considerations: Read this IBM support document.
  
  
• IBM Hardware Management Console Best Practices: This document provides a compilation of useful information, recommendations, and best practices for managing the HMC.
  
  
• Virtual I/O Server documentation: Get VIO Server documentation from the IBM Virtual I/O Server home page.
  
  
• Visit the IBM System p and AIX Information Center.
  
  
• IBM Rebooks: Read the following rebooks:
  • Advanced POWER Virtualization on IBM System p5
  • Partitioning Implementations for IBM eServer System p5 Servers
  
  
• The AIX and UNIX developerWorks zone provides a wealth of information relating to all aspects of AIX systems administration and expanding your UNIX skills.
  
  
• New to AIX and UNIX: Visit the New to AIX and UNIX page to learn more about AIX and UNIX.
  
  
• poweraix.org: Be sure to take advantage of poweraix.org, an information hub of the power AIX community comprising of user communities, partners, IT professionals and business users.
  
  
• developerWorks technical events and webcasts: Stay current with developerWorks technical events and webcasts.
  
  
• AIX 5L Wiki: Visit this collaborative environment for technical information related to AIX.
  
  
• Podcasts: Tune in and catch up with IBM technical experts.
  
  

Get products and technologies

• IBM trial software: Build your next development project with software for download directly from developerWorks.
  
  

Discuss

• Participate in the AIX and UNIX forums:
  • AIX 5L -- technical forum
  • AIX for Developers Forum
  • Cluster Systems Management
  • IBM Support Assistant
  • Performance Tools -- technical
  • Virtualization -- technical
  • More AIX and UNIX forums
  
  

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Table of contents

• What is logical partitioning?
• A special kind of LPAR: Virtual I/O Server
• Additional hardware needed
• Dynamic logical partitoning
• Preliminary considerations
• Creating the VIO Server
• Creating an AIX partition
• Configuring virtual SCSI devices in the VIO server
• Conclusion
• Resources
• About the author
• Comments

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