Power Systems High Availability & Disaster Recovery

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1 Power Systems High Availability & Disaster Recovery Solutions Comparison of various HA & DR solutions for Power Systems Authors: Carl Burnett, Joe Cropper, Ravi Shankar Table of Contents 1 Abstract Introduction to Cluster vs. VM Restart HA/DR models New HA/DR offerings for Power Systems in PowerVC Availability Features Geographically Dispersed Resiliency (GDR) Disaster Recovery Deployment guidelines High Availability Disaster Recovery References Abstract There are many elements to consider as you plan high availability and disaster recovery solutions for your Power Systems environment. In this article, we will explore some of these solutions and discuss some considerations and best practices when using technologies like PowerHA, Geographically Dispersed Resiliency and PowerVC within the data center. 2 Introduction to Cluster vs. VM Restart HA/DR models Business continuity is an integral part of any business operations. Almost all businesses have recovery plans in case of failures & disasters as downtime and disruptions to business could cause not only financial losses, but also public relations and trust in the business concerned. Power Systems has offered a rich set of HA & DR solutions over the years. A few more options have been added recently and this article provides an overview of various solu- Page 1 of 7

2 tions and how they compare with each other. We will also highlight tips and best practices if some of these solutions are used in parallel. Over the years clustering technologies have played an important role in regards to High Availability (HA) and Disaster Recovery (DR) operations. Clustering based HA or DR solutions rely on redundant standby nodes in the cluster to be able to take over the workload and start them when the primary node fails. Each node in the cluster will monitor health of various elements such as network interfaces, storage, partner nodes, etc. to act when any of these elements fail. Clustering technologies were the closest to fault tolerant environments in regards to HA or DR support based on completely redundant software and hardware components. Cluster solutions are often operating system or platform specific and they do provide detailed error monitoring, though they require considerable effort to deploy and maintain. Cluster DR model is highlighted in Fig 1 (displays DR solution, but applies to HA also except that in the case of HA no replication is involved) below and is contrasted with the other model that is popular in recent times. Fig 2 illustrates the VM restart based DR model. Here the entire VM (including system disk/rootvg, etc. and data disks) is replicated using storage replication methods. These copies of VMs are used during a disaster to start the VMs on the DR site. Operating systems in these VMs boot up and then workload is started to return to normalcy. This model is more suited for cloud deployments and can scale well to allow for DR management for the entire data center. VM restart based high availability involves very similar concept of restarting the VM/LPAR on some other host within a data center and relies on shared storage based image to start the VM. It is expected that Power deployments use both models of HA & DR as needed. Cluster based HA-DR solutions are best for protecting critical workloads. For example, SAP en- Page 2 of 7

3 vironments are distributed and cluster-based HA would be the best method to monitor and act for various components of the stack. For other workloads, a VM restart-based model might be sufficient protection for HA and DR. The following figure captures the level of HA/protection vs. complexity of implementation for these technologies. Fig 3: Complexity vs. coverage: Cluster HA/DR vs. VM Restart HA/DR 3 New HA/DR offerings for Power Systems in 2016 Power systems has introduced new offerings for HA and DR in 2016 that covers the spectrum of both models. A summary of the options is captured in the table below for PowerVM environments: Table 1: HA/DR solutions for Power Systems Cluster HA/DR solutions VM Restart HA/DR solutions High Availability Disaster Recovery AIX PowerHA SystemMirror for AIX 1. PowerVC Restart HA Geographically Dispersed IBM i PowerHA SystemMirror for IBM i 2. HMC Simplified Remote Resiliency (GDR) for Power 1 Linux 3 rd party cluster solutions restart 1: IBM i support expected in 2017 Cluster HA/DR solutions have existed for Power systems for a long time (PowerHA has been the leading HA/DR solution on AIX for more than 20 years). They have been enhanced recently to provide additional capabilities and user experiences. Please refer to reference #1 for more details. VM restart based HA/DR solutions are new in 2016 and are described below: Page 3 of 7

4 1. PowerVC High Availability Features: PowerVC added new capabilities around VM restart High Availability. These capabilities enable customers to deploy cloud environments easily and enable simplified High availability. 2. Geographically Dispersed Resiliency (GDR) Disaster Recovery: IBM introduced a new offering for disaster recovery using VM restart technology and storage mirroring. More details about these products are covered in the next few sections. 3.1 PowerVC Availability Features PowerVC provides enterprise virtualization and cloud management of Power Systems and leverages OpenStack to do so. PowerVC has introduced high availability management functions over its past few releases. Listed below is a summary of those features: One-click system evacuation During planned maintenance windows, this feature allows administrators to evacuate a host by leveraging live partition mobility (LPM). PowerVC orchestrates the mobility of all active VMs to other hosts in the environment (or a host of your choice), thereby allowing maintenance (e.g., firmware or VIOS updates, etc.) to be performed without disrupting workloads. While the host is in maintenance mode, PowerVC will not place any new VMs on this host either. Once maintenance is done, VMs can be then be placed on the host again and normal operation can resume. Automated remote restart PowerVC has supported PowerVM s simplified remote restart feature since its inception in the POWER8 timeframe. This feature allows an administrator to rebuild a VM residing on a failed host to a healthy host (assuming the hosts have shared storage). This is a critical availability feature as it provides a mechanism to recover critical VMs in the event their hosting server fails unexpectedly (read: unplanned outage). In PowerVC (released in December 2016), this process has been fully automated i.e., administrators can configure PowerVC to monitor hosts and perform this recovery step automatically, so even if a host becomes unavailable at 3 a.m. on a Saturday, you re still protected. Best of all, this can be configured with a few mouse clicks, so it s extremely simple! If your host is part of a PowerHA cluster, it is strongly recommended that you not enable automated remote restart for this host as well. You can still use automated remote restart for other hosts under PowerVC management, but be sure to exclude the respective hosts under PowerHA management. 3.2 Geographically Dispersed Resiliency (GDR) Disaster Recovery Page 4 of 7

5 Power systems now provides VM restart based DR solution for the entire data center. GDR integrates deeply with PowerVM environments (HMC, VIOS) to provide for DR restart of VMs across sites using storage replicated VM images. GDR Disaster Recovery solution is easy to deploy and manage. GDR can manage recovery of hundreds of VMs across the sites. Fig 4: GDR for simplified data center level Disaster Recovery For more details about GDR, please refer to reference #2. Some of the advantages of GDR are reflected in the following table: Table 2: Features of GDR Capability Customer Value Supports P7 & P8 Systems Support for AIX and Linux Guest VMS Enterprise Pool Support Daily validation Storage Replication Customization framework Easy to deploy Enables customer to move older P7 systems to DR site and pair with P8 in main data center DR for AIX and Linux (all major flavors) enables uniform DR solution for Power platform Flexible capacity management to reduce costs Early detection of faulty configuration and other issues Offloaded uniform data copy methods Plugin script to do custom checks every day and custom process events as they occur Less than 10 steps deployment enables simplified DR GDR can co-exist with other Power systems capabilities such as PowerVC, PowerHA SystemMirror (Standard Edition for High Availability), etc. if the administrator is aware of such a deployment and performs mutually exclusive operations. More details about these deployments are covered in the Deployment guidance section. Page 5 of 7

6 4 Deployment guidelines As described in the previous sections, Power systems offers both cluster and VM restart based HA/DR solutions. In the sections below, we will review how administrator can deploy these together in the same environment. One of the key principles to follow in regards to HA/DR deployments would be to ensure that not more than one orchestrator manages HA or DR for the VM concerned. That is, choose only one solution for HA or DR management of a VM. 4.1 High Availability Review your data center and categorize the workloads in various LPARs as critical and non-critical workloads. For critical workloads, you may decide to deploy PowerHA or other cluster based HA solution. Let us call these as the critical workload VMs. These LPARs should not be enabled for VM restart HA management of PowerVC. For other LPARs you may decide to use PowerVC as the VM restart-based HA manager. If you are doing so, using the PowerVC provided interfaces exclude the critical workload VMs from the HA management of PowerVC. Table 3: Cluster HA solutions vs. PowerVC HA management Critical Workloads/VMs Non-Critical Workloads PowerHA or other cluster HA solution (e.g., DB2 PureScale) Ö PowerVC HA management Ö 4.2 Disaster Recovery If you plan to implement cluster based DR solution (eg: PowerHA SystemMirror Enterprise Edition) for your critical workload VMs, then ensure that these VMs are not part of GDR disaster recovery management (GDR provides a mechanism to exclude the VMs from VM restart DR management) Note that GDR and PowerVC can co-exist. GDR will focus only on the manually triggered DR operations and will not interfere with any within the data center operations done by PowerVC in the active site. 5 References 1. PowerHA SystemMirror for AIX: v7.2 and Enhancements a. Health Dashboard b documentation 2. Introduction to GDR: a. GDR Wiki home b. Articles: i. Need for Business Continuity & introduction to GDR DR solution Page 6 of 7

7 ii. Optimize DR site resources using Enterprise Pool with GDR Disclaimers: This article is to provide an overview of the Power HA/DR solutions. All the information in this article is opinions from the authors and no way represents the position of IBM. Page 7 of 7