recvr point splitter enginuity 5876

White Paper

Abstract

This white paper explains the VMAX RecoverPoint splitter and other RecoverPoint features and functionality that are included in Enginuity 5876. May 2012

Symmetrix VMAX RecoverPoint Splitter and Enhancements in Enginuity 5876

2 Symmetrix VMAX RecoverPoint Splitter and Enhancements in Enginuity 5876

Copyright 2012 EMC Corporation. All Rights Reserved. EMC believes the information in this publication is accurate as of its publication date. The information is subject to change without notice. The information in this publication is provided as is. EMC Corporation makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose. Use, copying, and distribution of any EMC software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com. VMware and are registered trademarks or trademarks of VMware, Inc. in the United States and/or other jurisdictions. All other trademarks used herein are the property of their respective owners. Part Number H10641


Table of Contents

Executive Summary ................................................................................................. 4 Audience ............................................................................................................................ 4

The VMAX Splitter .................................................................................................... 4 Symmetrix splitter design ................................................................................................... 4 Zoning and masking ........................................................................................................... 5 Gatekeepers and RecoverPoint splitter control ................................................................... 5 Multiple Symmetrix splitters ............................................................................................... 6 Multiple RecoverPoint clusters ........................................................................................... 6 Mixing splitters................................................................................................................... 6 VAAI ................................................................................................................................... 7 Features and limitations ..................................................................................................... 7

Enhancements in 5876 Enginuity ............................................................................. 8 RecoverPoint settable device size and geometry................................................................. 8 Automatic Write-Protect Bypass (WPBP) ............................................................................. 8 Enhanced device tagging .................................................................................................... 8

Conclusion .............................................................................................................. 9


Executive Summary RecoverPoint provides continuous data protection and continuous remote replication for on-demand protection and recovery to any point in time. It supports advanced functionality, such as policy-based management, application integration, and WAN acceleration. RecoverPoint allows organizations to implement a single, unified solution to protect and/or replicate data across heterogeneous storage arrays. This leads to simplified management and a reduction in costs. RecoverPoint also provides the ability to recover data at a local or remote site at any point in time, and ensures continuous replication to a remote site without any performance impact on the production hosts.

Audience

This white paper is intended for the technology professional who needs to implement an advanced local or remote replication solution in an EMC or heterogeneous storage environment. It is specifically targeted at EMC customers who need to understand the new VMAX RecoverPoint Splitter and miscellaneous enhancements available in Enginuity 5876.

The VMAX Splitter The RecoverPoint Symmetrix array-based splitter is supported on VMAX, running Enginuity 5876 and RecoverPoint 3.5 and higher.

Symmetrix splitter design In RecoverPoint, the function of the splitter is to split application writes so that they are simultaneously sent to their local volumes and the RPA (RecoverPoint Appliance). The RPA then forwards the write to the target device in the remote array.

The Symmetrix splitter is based on Open Replicator. Open Replicator is a component of EMC Solutions Enabler which is the command-line-interface software suite used for managing a Symmetrix storage environment. It is also part of Symmetrix Enginuity.

When Open Replicator functions as a splitter, RecoverPoint acts as the remote array and presents virtual remote devices to Open Replicator. This allows the RPA to acknowledge writes to the remote devices, which, in RecoverPoint terminology, are called replica volumes. For more information about Open Replicator, refer to the EMC Solutions Enabler Symmetrix Migration CLI Product Guide.

To be replicated with the VMAX RecoverPoint splitter, a volume must be identified to the Symmetrix array as a RecoverPoint device. Device tagging informs the Symmetrix array that the device is reserved for RecoverPoint replication. Untagged devices are not allowed to create Open Replicator sessions with RecoverPoint.


Tagged devices are protected by the Symmetrix array in the following ways:

Tagged devices cannot be replicated by SRDF and cannot be the target of a TimeFinder operation.

The Symmetrix Management Console issues a warning if an attempt is made to change the configuration of tagged devices.

Solutions Enabler SYMCLI requires a force option to be used if configuration changes are made to tagged devices.

When a RecoverPoint consistency group is enabled, an Open Replicator RecoverPoint session is created for each production volume within that consistency group. Open Replicator RecoverPoint sessions are not created for the replica volumes until image access is enabled. And even after image access is disabled, stopped Open Replicator RecoverPoint sessions remain for each replica volume. Both production and replica Open Replicator RecoverPoint sessions are removed when their consistency group is disabled.

Configuration changes cannot be made to a device in an Open Replicator RecoverPoint session. For example, a device cannot be mapped or unmapped until the consistency group is disabled. Also, a device in an Open Replicator RecoverPoint session cannot be untagged.

Zoning and masking When an incoming host write is split, the splitting occurs at the FA port. When a host writes to a LUN through a specific FA port, the same FA port must forward the write to an RPA. Therefore, all RPAs must be zoned to the same FA ports as the hosts. For the same reason, the LUNs must be mapped and masked to the host and the RPAs through the same FA ports. Journal volumes, repository, and gatekeepers may use dedicated FA ports. In most implementations, best practice is to create a single zone in each fabric containing all of the RPA Fibre channel ports and the Symmetrix FA ports involved in RecoverPoint operations.

Gatekeepers and RecoverPoint splitter control

Because the VMAX RecoverPoint splitter is based on Open Replicator, RecoverPoint manages the Symmetrix splitter using Solutions Enabler. Solutions Enabler control commands are sent to the Symmetrix array by way of gatekeepers, which are small, three-cylinder devices (approximately 3 MB). RecoverPoint site control manages the resources of the RecoverPoint cluster, including the Symmetrix splitter. The active instance of the RecoverPoint cluster site control can only run on either RPA1 or RPA2, even if there are more RPAs in the cluster. As a result, the gatekeepers must only be presented to RPA1 and RPA2. RPA1 must have access to eight gatekeepers; RPA2 must have access to eight different gatekeepers. Individual gatekeepers must not be shared with any other RPA or host, and RPAs must have access to their gatekeepers by way of multiple redundant paths. If a site comprises multiple Symmetrix splitters, or multiple RecoverPoint clusters, a total of 16 gatekeepers is required for each Symmetrix-splitter/RecoverPoint-cluster combination.


Multiple Symmetrix splitters A single RecoverPoint cluster will support up to six Symmetrix splitters.

Multiple RecoverPoint clusters The Symmetrix array can function as a splitter for up to four RecoverPoint clusters. The following rules apply:

Open Replicator sessions for all RecoverPoint clusters count toward the maximum number of sessions supported by a Symmetrix splitter, which is 2,048.

For example, if cluster #1 is replicating 1,750 LUNs, and cluster #2 is replicating 2,000 LUNs, only an additional 346 sessions would be available across all clusters serviced by the splitter instance. These sessions apply to RecoverPoint only and have no impact on the supported number of non-RecoverPoint Open Replicator sessions that may be created in the Symmetrix.

A LUN may be accessed by only one cluster.

Site names must be unique for all RecoverPoint clusters sharing one Symmetrix splitter.

As an example of the previous two bullets:

o Cluster #1 is replicating between New York and London

o Cluster #2 is replicating between New York and San Francisco

o Both clusters use the same Symmetrix splitter in New York

In the New York site, the two clusters must have different names, such as NewYork1 and NewYork2. In addition, the same LUN cannot be replicated from New York to both London and San Francisco.

Mixing splitters RecoverPoint supports mixing the Symmetrix splitter and other splitters within the same RPA cluster at the same site, subject to the following limitations:

Each volume can be attached to only one splitter.

All volumes that belong to a given consistency group at a given copy must be attached to the same type of splitter. For example, for volumes of the same consistency group at the same copy, you cannot attach some volumes to a host-based splitter and others to a Symmetrix splitter. However, a consistency group at the same copy can span multiple Symmetrix splitters.

There are no limitations regarding the mixing of splitters across separate RPA clusters or sites. For instance, CRR replication can take place between a site that uses Cisco SANTap splitters and a site that uses Symmetrix splitters.


VAAI VMware vSphere 4.1 introduces vStorage API for Array Integration (VAAI). VAAI commands are designed to speed up certain operations when a VMware ESX server writes to a storage array by offloading specific functions to array-based hardware.

The Symmetrix splitter fully supports hardware-assisted locking. Hardware-assisted locking is a LUN locking mechanism that is more efficient in the clustered host environment. Hardware-assisted locking is also called Atomic Test and Set (ATS) and is implemented using the SCSI Compare and Swap command (CAS). If the CAS command results in a write, the splitter sends the copy of the write to RecoverPoint.

All other VAAI commands are rejected by the Symmetrix splitter; however, VAAI does not need to be disabled on the ESX server. When the Symmetrix splitter rejects a VAAI command, VMware immediately reverts to legacy behavior with no risk to data or performance.

For more information about RecoverPoint support of VAAI commands, including other splitters, refer to EMC RecoverPoint Replicating VMware Technical Notes.

Features and limitations

The Symmetrix splitter requires RecoverPoint 3.5 and higher and VMAX Series array.

LUNs up to 32 TB are supported.

At every site that runs the Symmetrix splitter, Gen4 hardware is required for RPA1 and RPA2, which are the appliances that run site control. RPA3RPA8 may be Gen3. RecoverPoint 3.4 and higher require Gen3 RecoverPoint appliances and higher.

Symmetrix splitter supports a maximum of 4096 Open Replicator sessions for RecoverPoint. In other words, the total number of production and replica volumes cannot exceed 4096 per array.

For example, if replicating between different storage arrays, 4096 replication sets can be created. However, if replicating locally to the same array, only 2048 replication sets can be created, because each set consumes two Open Replicator sessions on that array. If the Symmetrix splitter is shared between multiple RecoverPoint clusters, the sum of sessions of all clusters cannot exceed 4096.

RecoverPoint virtual image access and virtual image access with roll are not supported by Symmetrix splitters. Use logged (physical) image access instead.

The Symmetrix splitter does not support hosts connected by way of iSCSI.

The Symmetrix splitter does not support direct attach (switchless) configuration, since both the RPA and host must access the same FA port.

The Symmetrix splitter does not support Fibre Channel over Ethernet (FCoE).

VMAX arrays support a maximum of 512 initiators (hosts HBAs, plus RPA fibre channel ports) per FA port.


For example, an 8-node RecoverPoint cluster (16 Fibre Channel ports per fabric), plus 124 hosts with 4 HBAs per fabric (total 496 ports per fabric), will consume the maximum number of supported initiators.

VMAX Series arrays support 4092 devices per FA (two ports). A Symmetrix metadevice contains multiple meta members. Each meta member counts towards the maximum number of devices.

Enhancements in 5876 Enginuity The following are the RecoverPoint enhancements added to 5876 Enginuity.

RecoverPoint settable device size and geometry RecoverPoint has the ability to change native VMAX disk geometry and size in replication sets that

contain replica devices with different sizes and disk geometries than the production devices. This is typically required in environments where data is replicated between heterogeneous storage arrays. This is because devices on different types of storage arrays will not have exactly equal device sizes at the block level because of the way that geometry is set and cylinders are allocated when devices are created. RecoverPoint detects the differences between the devices and reduces the larger devices in the replica set in order that the devices are a common size. This allows replication from smaller to larger devices.

Automatic Write-Protect Bypass (WPBP) Replica volumes must be write-disabled, except during image access, when the replica is being accessed by a host and replication is disabled. When replication is enabled, the splitter sets target devices to be write-disabled to prevent conflicting writes to the replica from both the source LUN and from the host. Because RecoverPoint appliances need to be able to distribute replicated data to the replica volumes, they need to accept incoming writes from the splitter. Write Protect Bypass (WPBP) is an initiator group flag that allows the appliances to write to otherwise write-protected devices. Previously, this was a manual operation, but now it is handled dynamically by RecoverPoint, requiring no additional action by the user.

Enhanced device tagging Prior to 5876 Enginuity, all devices in the SAN visible to the RPAS were imported for potential use into the RecoverPoint GUI. This caused possible confusion for users because devices that were not tagged for RecoverPoint, or tagged devices that were in use on another cluster, were available for selection. To alleviate this potential issue, two new tagging features have been introduced: cluster tagging and tagged device filtering.


Cluster tagging: Symmetrix devices have a metadata area that is now used by RecoverPoint to label the device with a cluster CRC and other information RecoverPoint needs to store for its own use. This protects devices belonging to a cluster from being displayed in the RecoverPoint GUI as available devices and accidently used in other RecoverPoint clusters. The cluster name is set on the device once it is selected by the user for addition to a cluster.

Tagged device filtering:

RecoverPoint applies filtering to RecoverPoint-tagged devices in order that the devices and the clusters to which they belong can be clearly seen in the GUI. This eliminates user error by preventing devices from being displayed that are not part of a specific cluster view.

Conclusion RecoverPoint provides continuous data protection and continuous remote replication that allows users to recover to any point in time. Functionality such as policy-based management, application integration, and WAN acceleration exist in all RecoverPoint implementations and configurations. RecoverPoint can help simplify management and reduce costs by allowing organizations to implement a single, unified solution to protect and/or replicate data across heterogeneous storage arrays. 5876 Enginuity introduces the Symmetrix splitter to VMAX Series arrays. The Symmetrix splitter is based on Open Replicator, which is part of Symmetrix Enginuity and is also part of Solutions Enabler, which is the command-line-interface software suite used for managing a Symmetrix storage environment.

Along with the Symmetrix splitter, other enhancements in 5876 Enginuity have been added to increase the usability and functionality of RecoverPoint.

recvr point splitter enginuity 5876

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