IP quorum application configuration
The IP quorum application is a Java™ application that runs on a separate server or host. An IP quorum application is used in Ethernet networks to resolve failure scenarios where half the nodes or enclosures on the system become unavailable. In this scenario, the application determines which nodes or enclosures can continue processing host operations and avoids a split system, where both halves of the system continue to process I/O independently.
An IP quorum application can also act as the quorum device for systems that are configured with a single-site or standard topology that does not have any external storage configured. The IP quorum mode is set to Standard when the system is configured for standard topology; the quorum mode of Preferred or Winner is only available if the system topology is not set to standard. To change the quorum mode for the IP quorum application, select and set the mode to Preferred or Winner or use the chsystem command. This configuration gives a system tie-break capability, automatically resuming I/O processing if half of the system's nodes or enclosures are inaccessible.
On systems that support multiple-site topologies, you can specify which site resumes I/O after a disruption based on the applications that run on the site or other factors like whether the environment uses a third site for quorum management. For example, you can specify whether a selected site is the preferred for resuming I/O or if the site automatically "wins" in tie-break scenarios. If only one site runs critical applications, you can configure this site as preferred. During a disruption, the system delays processing tie-break operations on other sites that are not specified as "preferred". The designated preferred site becomes more apt to resume I/O and critical application remain online. If the preferred site is the site that is disrupted, the other site continues to win the tie-breaks and continue I/O. This feature only applies to IP quorum applications. It does not apply to Fibre Channel based third site quorum management. In stretched configurations or HyperSwap® configurations, an IP quorum application can be used at the third site as an alternative to third-site quorum disks. No Fibre Channel connectivity at the third site is required to use an IP quorum application as the quorum device. If you currently have a third-site quorum disk, you must remove the third site before you use an IP quorum application.
There are strict requirements on the IP network and some disadvantages with using an IP quorum application. When certain aspects of the system configuration change, an IP quorum application must be reconfigured and redeployed to hosts. These aspects include adding or removing a node (or hot-spare node) from the system or when service IP addresses are changed on a node. Other examples include changing the system certificate or experiencing an Ethernet connectivity issue. An Ethernet connectivity issue prevents an IP quorum application from accessing a node that is still online. If an IP application is offline, the IP quorum application must be reconfigured because the system configuration changed. To view the state of an IP quorum application in the management GUI, select You can also use the lsquorum command to view the state of the IP quorum application.
.Even with an IP quorum application at the third site, quorum disks at site one and site two are required, as they are used to store metadata that restores system configuration during failure scenarios. Quorum disks for each site are selected automatically and can be configured in the management GUI by selecting You can also use the chquorum command to assign MDisk as a quorum disk. .
The maximum number of IP quorum applications that can be deployed on a single system is five. Only one instance of the IP quorum application per host or server is supported. IP quorum applications on multiple hosts or servers can be configured to provide redundancy. If you have multiple Spectrum Virtualize systems in your environment, more than one IP quorum application is allowed per host, but each IP quorum instance must be dedicated to a single Spectrum Virtualize system within the environment. In addition, the host or server requires available bandwidth to support multiple IP quorum instances. Use the following network requirements to determine bandwidth and latency needs in these types of environments. The recommended configuration remains a single IP quorum application per host or server.
Do not deploy the IP quorum application on a host that depends on storage that is presented by the system. This action can result in a situation where the nodes need to detect the IP quorum application to process I/O, but cannot because the IP quorum application cannot access storage.
IP quorum requirements
Java Vendor and Version | ||||
Operating System | IBM | OpenJDK | Oracle | |
7.1 | 8 | 7-14 | 7-14 | |
AIX7.x | X | X | ||
RHEL6.x | X | X | X | X |
RHEL7.x | X | X | X | X |
RHEL8.x | X | X | X | X |
SLES11.x | X | X | X | X |
SLES12.x | X | X | X | X |
SLES15.x | X | X | X | X |
CentOS6.x | X | X | ||
CentOS7.x | X | X | ||
CentOS8.x | X | X | ||
Win2008x | X | X | X | |
Win2012x | X | X | X | X |
Win2016x | X | X | X | X |
Win2019 | X | X |