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EMC WHITE PAPER

EMC® VPLEX® WITH RED HAT HIGH AVAILABILITY ADD-ON BEST PRACTICES PLANNING

ABSTRACT

This White Paper provides a best practice to install and configure Red Hat High Availability Add-On with EMC VPLEX.

March 2016

2 EMC VPLEX with Red Hat High Availability Add-On Best Practices Planning

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Table of Contents

Executive summary.................................................................................................. 4 Introduction ....................................................................................................................... 4 Audience ............................................................................................................................ 4

VPLEX overview ....................................................................................................... 4 VPLEX family ....................................................................................................................... 5

VPLEX features ............................................................................................................... 6 Data mobility .................................................................................................................. 6 Continuous availability ................................................................................................... 6 Geographically dispersed clusters .................................................................................. 6 HA Infrastructure ............................................................................................................ 7 Migrations ...................................................................................................................... 7 Federated AccessAnywhere ............................................................................................ 7 VPLEX Witness ................................................................................................................ 8

VPLEX clustering architecture ............................................................................................. 9

Multipath .............................................................................................................. 11 DM-Multipath ................................................................................................................... 11 EMC PowerPath ................................................................................................................ 11

Red Hat High Availability Add-On overview ............................................................. 12

Business imperative for geographically dispersed clusters ..................................... 12

Red Hat High Availability Add-On with VPLEX .......................................................... 13 Planning Red Hat High Availability Add-On topology configuration ................................... 13 Best practices .................................................................................................................. 17

Global File System ................................................................................................. 18

Red Hat Enterprise Linux Virtualization ................................................................... 19 RHEV with cluster benefit ............................................................................................. 19

Conclusion ............................................................................................................ 19

References ............................................................................................................ 20


Executive summary High availability is an important business consideration. For many business applications, highly reliable and redundant hardware provides sufficient uptime. For other business needs, the ability for a critical application to fail over to another server in the same data center is sufficient. However, neither of these server availability strategies will help in the event of truly catastrophic server loss.

For some business applications, even an event as unlikely as a fire, flood, or earthquake can pose an intolerable amount of risk to business operations. For truly essential workloads, distance can provide the only hedge against catastrophe. By failing server workloads over to servers separated by hundreds of miles, truly disastrous data loss and application downtime can be prevented.

EMC® VPLEX® with High Availability Add On for Red Hat Enterprise Linux provides the answer.

Introduction This white paper discusses the VPLEX models and features to provide high availability data across geographically dispersed locations. It describes which technologies work together providing fully-automated failover mechanisms designed to protect customer data and provide data mobility for planned or unplanned downtimes.

Audience This white paper is intended for technology architects, storage administrators, and system administrators who are responsible for architecting, creating, managing IT environments that utilize EMC VPLEX technologies. The white paper assumes the reader is familiar with Linux Red Hat.

VPLEX overview EMC VPLEX delivers data mobility and availability across arrays and sites. VPLEX is a unique virtual storage technology that enables mission-critical applications to remain up and running during any of a variety of planned and unplanned downtime scenarios. VPLEX permits painless, non-disruptive data movement, taking technologies like Red Hat and other clusters that were built assuming a single storage instance and enabling them to function across arrays and across distance.

Figure 1 provides an example of an EMC GeoSynchrony™ operating environment.


Figure 1. GeoSynchrony operating environment

This section contains the following information:

• VPLEX family • VPLEX features • VPLEX clustering architecture

VPLEX family

The following are the EMC VPLEX family offerings:

• VPLEX Local: VPLEX local allows centralized management of all arrays in the data center. Storage management is simplified allowing for improved storage utilization across all storage arrays. Data mobility and availability is enhanced using VPLEX local.

• VPLEX Metro/Metro Express: VPLEX Metro uses EMC Federated AccessAnywhere™ technology, allowing block level access to data between two sites within synchronous distances. VPLEX Metro with its active/ active configuration provides high levels of availability, mobility and resource utilization between data centers. EMC VPLEX Metro Express Edition is preconfigured for mid-sized requirements, packaging VPLEX hardware and software in combination with EMC RecoverPoint continuous data protection (CDP). VPLEX Metro Express includes all functionality and features found in standard EMC VPLEX Metro. It comprises everything needed to build a two-site VPLEX Metro configuration for up to 40 TB.


Figure 2 provides an example of the VPLEX family offerings.

Figure 2. VPLEX offerings

VPLEX features

This section describes VPLEX features used in this paper.

Data mobility

Move applications, virtual machines, and data in and between data centers without impacting users.

Figure 3. Data mobility example

Continuous availability

Deliver application and data availability within the data center and over distance with full infrastructure utilization and zero downtime.

Figure 4. Continuous availability example

Geographically dispersed clusters

Server clusters support a single cluster spanning multiple sites.

Figure 5. Geographically dispersed clusters example


HA Infrastructure

HA Infrastructure reduces recover time objective (RTO).

Figure 6. HA infrastructure example

VPLEX is inherently a high availability solution that provides application and data mobility. Adding Red Hat High Availability Add-On to the VPLEX storage solution creates a total high availability environment with storage, servers, and application protection.

Migrations

Non-disruptive data migrations enable risk-free, faster tech refreshes and load balancing.

Figure 7. Migrations example

Federated AccessAnywhere

VPLEX utilizes cache coherency technology, Federated AccessAnywhere, EMC’s break-through technology that enables a single copy of data to be shared, accessed, and relocated over distance and between sites. Data is presented consistently across VPLEX clusters and can be accessed, shared or relocated between sites.


Figure 8. Federated AccessAnywhere example

VPLEX Witness

VPLEX Witness is an optional, but highly-recommended, component designed for deployment in customer environments where the regular bias rule sets are insufficient to provide seamless zero or near-zero Recovery Time Objective (RTO) failover in the event of site disasters and VPLEX cluster failures.

By reconciling its own observations with the information reported periodically by the clusters, VPLEX Witness enables the cluster(s) to distinguish between inter-cluster network partition failures and cluster failures and to resume I/O automatically in these situations.

Figure 9. High-level VPLEX Witness architecture


VPLEX clustering architecture

EMC VPLEX represents the next-generation architecture for data mobility and information access. The new architecture is based on EMC’s more than 20 years of expertise in designing, implementing, and perfecting enterprise-class intelligent cache and distributed data protection solutions.

As shown in the following figure, VPLEX is a solution for federating both EMC and non-EMC storage. VPLEX resides between the servers and heterogeneous storage assets and introduces a new architecture with unique characteristics:

• Scale-out clustering hardware, which lets customers to start small and grow big with predictable service levels

• Advanced data caching utilizing large-scale SDRAM cache to improve performance and reduce I/O latency and array contention

• Distributed cache coherence for automatic sharing, balancing, and failover of I/O across the cluster

• Consistent view of one or more LUNs across VPLEX clusters separated either by a few feet with a data center or across synchronous distances, enabling new models of high availability and workload relocation

Figure 10. Capability of the VPLEX system

VPLEX uses a unique clustering architecture to help customers break the boundaries of the data center and allow servers at multiple data centers to have concurrent read and write access to shared block storage devices. A VPLEX cluster can scale up through the addition of more engines, and scale out by connecting multiple clusters to form a VPLEX Metro configuration.

In the initial release, a VPLEX Metro system supports up to two clusters, which can be in the same data center or at two different sites within synchronous distances (approximately up to 60 miles or 100 kilometers apart).

VPLEX Metro configurations help users to transparently move and share workloads, consolidate data centers, and optimize resource utilization across data centers.


In addition, VPLEX clusters provide nondisruptive data mobility, heterogeneous storage management, and improved application availability.

Figure 11. Schematic representation of supported EMC VPLEX cluster configurations

A VPLEX cluster is composed of one, two, or four engines. The engine is responsible for virtualizing the I/O stream, and connects to hosts and storage using Fibre Channel connections as the data transport. A single-engine VPLEX cluster consists of the following major components:

• Two directors, which run the GeoSynchrony software

• Dedicated 8 Gb FC front-end, back-end, and local COM and WAN ports

• One Standby Power Supply, which provides backup power to sustain the engine through transient power loss

Each cluster also consists of:

• A management server that provides a GUI and CLI interface to manage a VPLEX cluster

• An EMC standard 40U cabinet to hold all of the equipment of the cluster

Additionally, clusters containing more than one engine also have:

• A pair of Fibre Channel switches used for inter-director communication between various engines

• A pair of Universal Power Supplies that provide backup power for the Fibre Channel switches and allow the system to ride through transient power loss


Multipath Both Linux native DM-Multipath and EMC PowerPath are supported by EMC VPLEX when configured with Red Hat High Availability Add-On.

DM-Multipath

Device mapper multipathing (DM-Multipath) is the Linux native multipath software which can configure multiple I/O paths between server nodes and storage arrays into a single device.

DM-Multipath can be used to provide:

• Redundancy

DM-Multipath can provide failover in an active/active configuration. In an active/active configuration, if any element of an I/O path (the cable, switch, or controller) fails, DM-Multipath switches to an alternate path.

• Improved Performance

DM-Multipath can be configured in active/active mode, where I/O is spread over the paths in a round robin fashion. In some configurations, DM-Multipath can detect loading on the I/O paths and dynamically re-balance the load.

When using DM-Mulitpath, consult Red Hat’s DM Multipath, available at: https://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/?locale=en-US.

EMC PowerPath

PowerPath is host-based software that provides automated data path management and load-balancing capabilities for heterogeneous server, network, and storage deployed in physical and virtual environments. It provides the following benefits:

• Automates failover/recovery

PowerPath automates data path failover and recovery to ensure applications are always available and remain operational.

• Optimizes load balancing

Adjusts I/O paths constantly to leverage all available data paths and to monitor and rebalance the dynamic environment for the best application performance.

• Standardizes path management

Simplifies and standardizes data path management across heterogeneous physical and virtual environments as well as cloud deployments.

For steps on how to install and configure PowerPath, refer to one of the following EMC PowerPath documents available at https://support.emc.com:

− PowerPath for Linux 6.0 Installation and Administration Guide

https://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/?locale=en-US

https://support.emc.com/


− PowerPath for Linux 6.1 and Minor Releases Installation and Administration Guide

Red Hat High Availability Add-On overview A failover cluster is a group of independent computers that work together to increase the availability and scalability of clustered roles (formerly called clustered applications and services). The clustered servers (called nodes) are connected by physical cables and by software. If one or more of the cluster nodes fail, other nodes begin to provide service (a process known as failover). In addition, the clustered roles are proactively monitored to verify that they are working properly. If they are not working, they are restarted or moved to another node.

The High Availability Add-On is an integrated set of software components that can be deployed in a variety of configurations to suit the needs for performance, high availability, load balancing, scalability, file sharing, and economy. For more details, please consult High Availability Add-On Overview, “High Availability Add-On Introduction” chapter, available at: https://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/?locale=en-US

Business imperative for geographically dispersed clusters Not all server workloads are created equal. Some applications and solutions hold disproportionate value to your organization. These might be the line-of-business application that represents your competitive advantage or the email server that ties your far-flung organization together. The dark side of these essential IT functions is that they provide a hostage to fate; eventually something will take those services offline, severely hampering your company’s ability to operate, or even bringing business operations to a halt.

Redundant hardware on servers, redundant servers at data centers, and effective IT management all play a role in keeping these applications online and available to your employees and your customers. However, none of these precautions can prepare for large-scale server disruptions. Fires, floods, and earthquakes that can destroy or impair an entire data center are relatively rare, yet they do occur and, without adequate preparation, they can cost an organization millions of dollars in lost revenue and production. For truly large disasters, distance between server sites is the only thing that can keep a disruption from turning into a catastrophe.

Geographically dispersed clusters can form an important component in disaster preparation and recovery. In contrast to cold standby servers, the servers in a multi-site cluster provide automatic failover. This reduces the total service downtime in the case of a loss of a business-critical server. Another server in the cluster takes over service from the lost server as soon as the cluster determines that it has lost communication with the server previously running the critical workload, as opposed to users and customers waiting for human administrators to notice the service failure



and bring a standby server online. And, because the failover is automatic, it lowers the overall complexity of the disaster-recovery plan.

The lower complexity afforded by automatic failover in a multi-site cluster also reduces administrative overhead. Changes made to applications and the application data housed on the cluster are automatically synchronized between all of the servers in the cluster. Backup and recovery solutions do this with a periodic snapshot of the standalone server being protected; meaning that the standby server may have a longer effective time to recovery. For example, if the backup software takes a snapshot every 30 minutes, even if the standby server is brought online at the disaster recovery site within 10 minutes, if the last 25 minutes of transactions have been lost with the primary server, the recovery might as well have taken 25 minutes (at least from the user’s point of view).

Red Hat High Availability Add-On with VPLEX EMC VPLEX in a clustered storage configuration may present devices that are distributed across the two VPLEX sites. Coherency is provided through a WAN link between the two sites such that if one site should go down, the data is available from the other site. Further high availability for the data center is achievable through server clustering. Red Hat High Availability Add-On is supported in such an application.

This section discusses how to plan Red Hat High Availability Add-On topology configuration and best practices.

Planning Red Hat High Availability Add-On topology configuration

VPLEX Local HA infrastructure provides applications highly reliable and redundant hardware while delivering data mobility and availability across arrays from both EMC and Non-EMC storage. You can manage heterogeneous block storage from a single interface with EMC Unisphere for VPLEX, which uses the same graphical user interface (GUI) framework as EMC VNX and EMC VMAX platforms, providing a way to simplify, normalize, and consolidate EMC management tools.


Figure 12 shows an example of Red Hat High Availability Add-On in a VPLEX Local configuration.

Figure 12. Red Hat High Availability Add-On in a VPLEX Local configuration

VPLEX Metro provides not only applications highly reliable and redundant hardware but also the distance that offers the only hedge against catastrophe. By failing server workloads over to servers separated by hundreds of miles, truly disastrous data loss and application downtime can be prevented.


Figure 13 shows an example of Red Hat High Availability Add-On in non-cross-cluster connected configuration.

Figure 13. VPLEX Metro in a non-cross-cluster connected configuration


Figure 14 shows an example of Red Hat High Availability Add-On in a cross-cluster connected configuration.

Figure 14. VPLEX Metro in a cross-cluster connected configuration


Best practices

Consider the following best practices.

Stretched storage cluster

All Red Hat stretched clusters require obtaining a formal architectural review from Red Hat Support to ensure that the deployed cluster meets established guidelines. Please refer to Red Hat knowledgebase for operating system caveats regarding Red Hat stretched cluster implementations:

https://access.redhat.com/site/node/27136

Heartbeat limitation

Server cluster heartbeat limitation per Red Hat specification is less than or equal to 2.0ms round trip time (RTT) latency.

Refer to Red Hat Knowledgebase Article ID: 58412 at:

https://access.redhat.com/site/node/27136

Consistency groups

Consistency groups should be set for one site wins for all distributed devices in the VPLEX metro cluster attached to the Red Hat High Availability Add-On cluster. The winning site should be aligned to the winning nodes in the Red Hat High Availability Add-On cluster.

Security

To allow the nodes in a cluster to communicate with each other, the IP ports assigned to Red Hat High Availability Add-On components should be enabled on every node. Please refer to Red Hat Cluster Administration, “Enabling IP Ports” chapter, located at the following site, to configure these security options for your environment:

https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Cluster_Administration/index.html

Quorum disk

A Red Hat High Availability Add-On quorum disk was qualified on a distributed device. If a quorum disk is configured under an EMC PowerPath pseudo device, it is recommended that the TOTEM TOKEN should be set at 330000ms. This is to protect against a worst case failure scenario regarding paths to the quorum disk. It is further recommended that if the recommended setting is not used; test your desired settings in a non-production environment before implementing them. If not, an unstable cluster may result.

https://access.redhat.com/site/node/27136#Supported_Use_Cases





If Red Hat’s native Linux DM-Multipath is used, please follow the guidance provided by Red Hat documentation for the cluster design employed.

Further guidance for Red Hat High Availability Add-On quorum disk can be found in Red Hat's How to Optimally Configure a Quorum Disk in Red Hat Enterprise Linux Clustering and High-Availability Environments, at:

https://access.redhat.com/documentation/en/red-hat-enterprise-linux

SCSI fencing

SCSI fencing is a shared storage device based fencing methodology that uses SCSI-3 persistent reservations to control access by the nodes in the cluster to the device. For a node to be able to use the device, it must first register with the device through the fence_scsi agent, then reserve the device preventing other nodes from accessing it at the same time.

For best practices to configure SCSI fence for PowerPath pseudo device with VPLEX, please review the “Supported Red Hat RHCS configurations and best practices” section in the EMC Host Connectivity Guide for Linux, available at https://elabnavigator.emc.com.

For best practices to configure SCSI fence for a Red Hat’s native Linux DM-Multipath device with VPLEX, please review the “SCSI Persistent Reservations” section in the Red Hat Enterprise Linux 6 Fence Configuration Guide or “Configuring Fencing using SCSI Persistent Reservations” in Red Hat Enterprise Linux 7 Configuration Example - Fence Devices Configuring Fence Devices in a Red Hat Cluster , found at:


Global File System The Red Hat GFS2 file system is included in the Resilient Storage Add-On. It is a native file system that interfaces directly with the Linux kernel file system interface (VFS layer). When implemented as a cluster file system, GFS2 employs distributed metadata and multiple journals. Red Hat supports the use of GFS2 file systems only as implemented in the High Availability Add-On.

While a GFS2 file system may be used outside of LVM, Red Hat supports only GFS2 file systems that are created on a CLVM logical volume. CLVM is included in the Resilient Storage Add-On. It is a cluster-wide implementation of LVM.

For more information, see Red Hat Enterprise Linux Global File System 2 at: https://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/?locale=en-US


https://elabnavigator.emc.com./




Red Hat Enterprise Linux Virtualization Red Hat Enterprise Virtualization (RHEV) is a complete enterprise virtualization management solution for server and desktop virtualization, based on Kernel-based Virtual Machine (KVM) technology.

Designed for enterprise-class scalability and performance, Red Hat Enterprise Virtualization enables management of your entire virtual infrastructure, including hosts, virtual machines, networks, storage, and users from a centralized graphical interface.

RHEV with cluster benefit

RHEV 3 supports clustered features, including:

• Live migration. Allows for running VMs to be moved seamlessly from one host to another within a Red Hat Enterprise Virtualization cluster.

• Storage live migration. Allows for a single or multiple concurrent running VM’s disk to be moved within the storage infrastructure, without interruption to users or the VM.

• High availability. Allows critical VMs to be restarted on another host in the event of hardware failure with three levels of priority, taking into account resiliency policy. Supports application-level high availability with supported fencing agents for Red Hat Enterprise Linux guests using the Red Hat Enterprise Linux High Availability Add-On.

For more details, please consult the Red Hat Enterprise Linux Virtualization Getting Started Guide at:


Conclusion

This document provided an overview introduction of EMC VPLEX, along with a best practice of installation and configuration of Red Hat High Availability Add-On with EMC VPLEX. For the host side, High Availability Add On for Red Hat Enterprise Linux provides customers a solution when some members of a cluster encounter unanticipated failure. The services can continue to run by relocating to the other member. For the storage side, the VPLEX can give customers not only the availability across arrays, but also data mobility, backups, and performance.



References

For more information, refer to the following documents, located at: https://support.emc.com • EMC Host Connectivity Guide for Linux • Implementation and Planning Best Practices for EMC VPLEX Technical Notes • EMC VPLEX with GeoSynchrony Product Guides

https://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/?locale=en-US • Red Hat Enterprise Linux Cluster Administration • Red Hat Enterprise Linux Fence Configuration Guide • Red Hat Enterprise Linux Virtualization Administration Guide • Red Hat Enterprise Linux High Availability Add-On Overview • Red Hat Enterprise Linux Virtualization Getting Started Guide • Red Hat Enterprise Linux Global File System 2 • Red Hat Enterprise Linux DM Multipath

The following documentation is also available:

• Using SCSI Persistent Reservations with Red Hat Enterprise Linux 6 https://access.redhat.com/site/articles/40112

• Support for Red Hat Enterprise Linux Cluster and High Availability Stretch Architectures https://access.redhat.com/site/node/27136

• RED HAT ENTERPRISE VIRTUALIZATION 3: An overview of product features and capabilities


https://support.emc.com/


https://access.redhat.com/site/articles/40112



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