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Introduction to Initiator Port Groups

By Shyama Venugopal posted Wed February 12, 2020 02:10 PM

Starting PowerVC 1.4.4, there is more flexibility for its users in choosing the right Fiber Channel port configuration to meet their needs. In the first of this blog series, you will get an overview of Initiator Port Groups and the different options available. The upcoming blogs will highlight how Initiator port group help solve few common problems around choosing FC ports per volume in PowerVC.

What are Initiator Port Groups (IPG)?

Storage Connectivity Groups are a means by which an administrator can define policies that control the placement of a workload [VM], ensuring that it has access to the required storage providers, where a storage provider is either a Shared Storage Pool (backed by a Virtual I/O Server Cluster) or a registered SAN Storage Controller. The main purpose of Storage Connectivity Groups is to isolate storage traffic for certain workloads to specific groups of Virtual I/O Servers. When a VM is deployed, you must specify a storage connectivity group.

Till 1.4.4, there was no way for a virtual machine to have volumes using different set of fibre channel ports. This meant all volumes attached to a virtual machine ‘always’ used the same set of host/initiator ports. Previously, you could add port tags for use with storage connectivity groups and to specify whether PowerVC can use/restrict the Fibre Channel ports used for deployments/attachments. Each volume attachment will always use all the FC ports with the right tag.

However, in some cases it is required to use different port for different volume attachments,
a. Isolating sets of FC ports based on storage provider. Eg., host ports p1, p2 for a volume from Storage1 and p3, p4 for volumes from Storage2.
b. Use different VFC adapter on the VIOS for different volumes. This enables attachment of higher number of volumes to a given VM.
c. Specific path between Host’s FC ports and Storage Ports (or Storage Port Groups)

Through initiator port groups PowerVC provides finer control over FC Ports.

Creating Initiator Port Groups in PowerVC

To create initiator port groups, perform the following steps:

  1. Navigate to Storage Connectivity Groups and scroll to the “Define Initiator Port Groups” section.

    [caption id="attachment_4179" align="aligncenter" width="666"] Initiator Port Groups[/caption]

  2. Select the “Define groups of VIOS FC ports allowed for I/O connectivity" checkbox.

  3. Click ‘Create’ for adding new Initiator port groups. The ‘Create’ dialog lists all the FC ports per host along with fabric and status information.

  4. Choose all the ports which must be part of the group.

    [caption id="attachment_4180" align="aligncenter" width="666"] Selecting port for IPG[/caption]

    The details of all Initiator port groups are listed in the SCG details page.

    [caption id="attachment_4181" align="aligncenter" width="666"] View the Initiator port group[/caption]

A few considerations:

  • An initiator port cannot be part of multiple groups.

  • Each host in the SCG must be represented in the Initiator port group. If there are no ports from a hostA in an Initiator group, then the volumes using this group cannot be migrated to hostA. On addition of new hosts, the Initiator port group must be edited to include the right ports. There is no auto-addition of ports into the Initiator group.

  • An Initiator Port Group can only be deleted when there are no VM using the SCG.

Choosing the initiators to be used for a volume attachment:

There are 3 different ways to choose the Initiator port group for a volume attachment.

  1. Using storage template to define the Initiator port group:
    A new section “Match Initiator PortGroups” has been introduced in Storage Template.
    a. Click on “Define path between storage port groups and initiator port group”. You can see a list of existing Initiator Port Groups defined on the SCG.
    [caption id="attachment_4182" align="aligncenter" width="666"] Choose IPG in storage template[/caption]
    b. Choose an IPG from the list or choose to define a new Initiator Port Group – and create it later in the SCG.

  2. Select the initiator port group based on Storage port group:

    Another method to specify the Initiator Port for a volume attachment is to match with the Storage Port Groups. With IBM based storages, you can define storage port groups(refer to blog on how to configure storage port groups).
    To connect initiator port groups to specific storage port groups, you must ensure,

    a. The names of initiator port groups and storage port groups are same:

    [caption id="attachment_4183" align="aligncenter" width="666"] Storage port group[/caption]
    b. The “Match Initiator port groups with Storage port groups defined above” checkbox is selected.

    [caption id="attachment_4184" align="aligncenter" width="666"] Match initiator and storage port group[/caption]

  3. Let PowerVC choose the initiator port group for a volume attachment.
    When there is no Initiator port group in the storage template, but there are IPG defined in the SCG, PowerVC picks the least used port group. Only the volume attachments done through PowerVC are taken into consideration here.

    Each of these methods would be described in detail in the upcoming blogs, as part of this series. We will delve into examples and solving different problems using Initiator Port Group in PowerVC.

To be continued...

If you have any questions about this topic, please comment below. We would love to hear from you. Watch this space for more information about troubleshooting your environment. In the meantime, don't forget to follow us on LinkedIn, Facebook, and Twitter

Blog authors:
1. Shyama Venugopal
2. Abhinav Shrivastava
1 comment



Thu December 31, 2020 04:45 AM

It looks the pictures were not migrated here from developerworks.