VMware Infrastructure Deployment with EMC® Celerra® Unified Storage

Applied Best Practices Guide

Copyright © 2009 EMC Corporation. All rights reserved. Published June, 2009 EMC believes the information in this publication is accurate as of its publication date. The information is subject to change without notice. Benchmark results are highly dependent upon workload, specific application requirements, and system design and implementation. Relative system performance will vary as a result of these and other factors. Therefore, this workload should not be used as a substitute for a specific customer application benchmark when critical capacity planning and/or product evaluation decisions are contemplated. All performance data contained in this report was obtained in a rigorously controlled environment. Results obtained in other operating environments may vary significantly. EMC Corporation does not warrant or represent that a user can or will achieve similar performance expressed in transactions per minute. No warranty of system performance or price/performance is expressed or implied in this document. 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. All other trademarks used herein are the property of their respective owners. Part number: H6370

VMware Infrastructure Deployment with EMC Celerra Unified Storage

Overview

Introduction This paper explores the benefits of using an EMC® Celerra® Unified Storage

Platform array as the shared storage component of a VMware Virtual Infrastructure (VI) environment. Learn to leverage Celerra for NAS, block storage, and more advanced features like replication, virtual provisioning, VMware Site Recovery Manager and primary storage deduplication in a VI3 environment.

Structure of this document

This white paper is divided into four major sections: • Protocols – storage protocols supported by the Celerra Unified Storage

Platform. These include: − File protocols: CIFS – Common Internet File System NFS – Network File System

− Block protocols iSCSI – Internet Small Computer Systems Interface FC – Fibre Channel

• File system enhancements – technologies to give Celerra greater storage efficiency. Topics discussed are: − Primary storage deduplication − Celerra Virtual Provisioning™ − CLARiiON® thin LUNs

• Backup – VMware backup methods using Celerra technologies. This covers: − NDMP – Network Data Management Protocol − Celerra Replicator™ − SnapSure™ file system snapshots

• Business continuity – Celerra features relating to protection of live data, which covers: − Celerra snapshots for both iSCSI and file systems − Celerra Replicator − VMware Site Recovery Manager (SRM)

For each section this paper will discuss relevant Celerra features and how they are implemented in a VMware environment.

Document scope

This paper gives a broad, initial overview of Celerra technologies and how they interact with and can be used in concert with VMware Virtual Infrastructure deployments. A basic understanding of VMware VI products and the EMC Celerra is assumed.

Intended audience

This document is intended for internal EMC personnel, EMC channel partners, and customers.

Contents This publication contains the following chapters:

Chapters See Page

Chapter 1 - Celerra Storage Protocols 3

Chapter 2 - Celerra File System Technologies 13

Chapter 3 - VMware Backup Options 18

Chapter 4 - Business Continuity Features of Celerra 20

Chapter 1 - Celerra Storage Protocols

Celerra storage protocols in a VMware environment

Introduction Clustered VMware environments make extensive use of shared storage over

many protocols. Each protocol has specific strengths that can be leveraged to provide superior levels of performance and scalability, depending on the application. The ability of the Celerra to support all major storage protocols allows for very flexible and high performance configurations, all on the same array. This chapter explores the benefits of Celerra as a provider of file and block level storage for a VI3 environment. More information about the Celerra hardware and software features is available at http://www.emc.com/products/family/celerra-family.htm.

Chapter terms Common Internet File System (CIFS) – An implementation of the Microsoft

Server Messaging Block (SMB) protocol. Server Messaging Block version 2 (SMBv2) –- Introduced with Microsoft Windows Vista and Windows Server 2008. Network File System (NFS) – A file sharing protocol developed for UNIX-like systems. Fibre Channel (FC) –A network technology primarily used for storage networking. Virtual Desktop Infrastructure (VDI) – The hosting and virtualization of a individual Client OS in a centralized location. Internet Small Computer Systems Interface (iSCSI) – An Internet Protocol (IP) based method of transferring SCSI traffic over a traditional Ethernet network. Export – A Celerra file system that is shared for use on the network. Uncached NFS Write – A configuration that allows well-formed writes (for example, writes that are disk block aligned or whose size equals a multiple of the Celerra disk block size) to be sent directly to the disk without being cached on the Celerra Data Mover. Data Mover – Special purpose servers in the Celerra that export data from the captive CLARiiON to clients on the network over CIFS, NFS, or iSCSI. Temporary Writeable Snap (TWS) – A writeable snapshot of an iSCSI LUN.

Contents This chapter contains the following topics:

Topic See Page

Common Internet File System (CIFS) 4

Network File System (NFS) 6

Fibre Channel 11

Common Internet File System (CIFS)

Introduction to CIFS

The Common Internet File System (CIFS) is an open implementation of Microsoft’s Server Messaging Block (SMB) protocol. With Windows Vista and Windows Server 2008, Microsoft added support for SMBv2, which has enabled advanced features designed to improve network performance over a WAN or LAN including: Request compounding - allows for multiple commands to be placed in a single packet. Request pipelining - a technique in which multiple requests are written out without waiting for the corresponding responses. Durable handles - allow an SMB2 connection to transparently reconnect to the server if there is a temporary loss of network connectivity.

Celerra CIFS support

The Celerra CIFS implementation adds support for SMBv2 in DART 5.6.42 and later. If SMBv2 is present on the Celerra it will attempt a SMBv2 type connection. If the client cannot support SMBv2, the Celerra will negotiate a SMBv1 connection to maintain backwards compatibility.

Using CIFS with VMware

VMware ESX does not directly support using CIFS shares for VMFS or virtual machine datastores. However, a VMware environment can benefit from leveraging CIFS on the Celerra by using it as a file share for network clients and servers. When combined with Celerra file system checkpoints, CIFS clients will be able to take advantage of the Previous Versions functionality in Windows that allows users to restore previous versions of files stored on the share. The graphic below highlights how components of a desktop in a VDI solution can be handled by a Celerra. The user’s My Documents and roaming profile data can be redirected to a CIFS export on the Celerra and CIFS can also be used for VMware ThinApp application distribution and network sandbox.

The Celerra can simultaneously support the CIFS, NFS, iSCSI and FC protocols, which makes it a compelling choice for environments that need the utmost flexibility at the storage array. Celerra is a natural fit for VDI deployments since it can provide all the storage components in one frame.

Network File System (NFS)

Introduction to NFS

Network File System (NFS) is a protocol originally developed by Sun Microsystems in 1984. NFS is most commonly used with UNIX-like systems and is the preferred network file protocol for VMware.

Celerra NFS support

Celerra NFS implementation supports: • NFS versions 2 – 4 • NFS file system checkpoints • Read-only exports • NIS/user-mapper integration • Nondisruptive file system extension Celerra also supports using uncached writes for NFS exports. This is designed to improve performance for applications with many connections to a large file. Since VMware stores many objects as large files, this option should be considered. Uncached writes can increase performance when accessing large files by 30 percent or more and is recommended when NFS is used for storing VMDK files. For more information on optimizing VMware VMware ESX with the Celerra please see the VMware ESX Optimization with EMC Celerra Performance Study Technical Note at: http://www.emc.com/collateral/hardware/technical-documentation/300-006-724.pdf

Using NFS with VMware

NFS is typically heavily leveraged in a VMware environment. Typical applications for an NFS export include: • ESX datastore • ISO or file repository Using NFS for an ESX datastore allows for very efficient allocation of storage on the array, since the NFS protocol is thinly provisioned by default. Data blocks in the file system are allocated to the NFS client only when they are needed. When leveraging thinly provisioned file systems on an NFS datastore, the default virtual machine disk type of zeroedthick should be used. Disks of the zeroedthick type do not preallocate space in the VMDK files during creation. VMs created in vCenter are this type by default. The eagerzeroedthick disk type should not be used as it writes zeroes to the entire allocated space in the VMDK file, causing the VMDK to consume its full capacity. This negates the benefits of a thin provisioned file system. The reference architecture shown next is a typical SQL Server 2005 virtualized infrastructure that uses NFS for the storage network.

For more sample reference architectures see http://www.emc.com/resource-library/.

A note about multi-protocol support

The Celerra has the ability to share a file system over both CIFS and NFS concurrently. This eliminates the need for an administrator to maintain and synchronize two separate file systems for users who need to access the same dataset from both Windows and UNIX clients concurrently.

Internet Small Computer Systems Interface (iSCSI)

Introduction to iSCSI

Internet Small Computer Systems Interface (iSCSI) embeds the feature and command set from the SCSI-3 protocol in TCP/IP (allowing the transmission of SCSI block level commands) over a standard Ethernet network. This allows for fast and efficient block level access to storage using an existing or dedicated gigabit IP network.

iSCSI features on Celerra

Celerra iSCSI LUNs are able to offer the following benefits: • Write-penalty free incremental copies • Up to 2,000 snapshots of an iSCSI LUN • Snapshots can be made writeable (TWS) • Snapshots support instant restore to a previous view of the file system • iSCSI LUN virtual provisioning

Using iSCSI in a VMware environment

Both Fibre Channel (FC) and iSCSI allow for block access to storage. iSCSI is used when FC is considered to be too expensive or complex for deployment. iSCSI allows for the use of the existing IP network and the expertise of network administrators to extend the SAN without in-house expertise in FC solutions. iSCSI LUNs can be masked directly to an ESX host (or cluster) for use as a VMFS datastore, which can host a number of virtual machines. Direct access to a LUN can be given to a virtual machine (VM) using the Microsoft Software iSCSI Initiator (MSI). This allows for solutions that require high performance storage and can be used to implement Exchange and SQL solutions as VMs. The following figure shows a virtualized Exchange 2007 infrastructure utilizing Celerra iSCSI for the storage network interconnects.

Celerra iSCSI TWS snapshots without VP

Temporary Writeable Snaps (TWS) and virtually provisioned iSCSI LUNs can be combined to realize enormous storage and cost savings in a VMware environment. In the following example, all iSCSI LUNs are thickly provisioned, which leads to 22 GB of storage consumed although only 6 GB has been written to the file system.

Celerra iSCSI TWS snapshots with VP

In the following example, all iSCSI LUNs are virtually provisioned (sparse), which leads to only 6 GB being consumed on the array. Only the amount of storage actually written by the host is consumed on the array.

Leveraging virtual provisioning allows the array to achieve high levels of utilization, which drives down the costs to acquire and maintain storage that is not being used. Space that would have normally been unavailable for use is now returned to the file system pool and can be allocated for other uses.

iSCSI use case iSCSI is the easiest and most cost-effective method for deploying block level

storage to ESX hosts. iSCSI represents the most flexible method of deploying block level storage to an ESX cluster while providing good performance over standard 1 Gb Ethernet. EMC has many white papers showcasing technologies like Microsoft Exchange and Microsoft SQL deployed on iSCSI, allowing high value, highly demanding workloads to be virtualized. These white papers are found at http://www.emc.com/solutions/. The ability to virtually provision writeable snapshots on the Celerra makes it an ideal platform for a VDI solution that uses array-based snapshots. For more information on using Celerra iSCSI snapshots for implementing VDI, see Scaling VDI without Scaling Cost at http://www.emc.com/events/online-event-presentations//2008/q1/03-19-08-vmware.pdf.

Fibre Channel (FC)

Introduction to Fibre Channel

Fibre Channel (FC) is a high speed network technology used to transport Fibre Channel Protocol (FCP) traffic on FC networks. FC offers a very high bandwidth and low latency network with speeds up to 8 Gb/s (at the time of publication). FC is usually used when applications or servers require the highest performance interconnects into the SAN.

FC features on Celerra

The Celerra Unified Storage Platform exposes the FC interfaces of the captive EMC CLARiiON to hosts. In doing so, the Celerra provides all the capabilities of the CLARiiON for use by VMware. The CLARiiON provides the underlying storage for the Celerra file systems that will be exported as CIFS, NFS or iSCSI storage.

Using FC with VMware

Use cases for FC storage include: • VMFS volumes that will need the highest performance for intensive

virtualized workloads • ESX boot LUNs that allow the VMware ESXs to boot from the SAN,

eliminating disks in the servers. This cuts acquisition and maintenance costs of the servers.

With the release of VMware View 3 with View Composer, FC datastores can be used for VDI deployments by leveraging linked clones on an FC datastore. This allows the VM boot volumes to be located on FC storage if needed. The following figure shows how the Celerra works with the CLARiiON to provide the storage for an Oracle RAC solution. The Celerra is providing the NFS export for the “flash” and “arch” file systems while the CLARiiON is providing the FC storage for all other file systems.

Chapter 2 - Celerra File System Technologies

Leveraging Celerra file system technologies

Introduction This chapter explores technologies that augment the Celerra file system by

providing advanced features like virtual provisioning and deduplication.

Contents This chapter contains the following topics:

Topic See Page

Deduplication 14

Celerra Virtual Provisioning 16

Clariion Thin LUNs 17

Deduplication

Introduction to data deduplication

The main objective of data deduplication is to increase file storage efficiency by eliminating redundant data from files located on the storage array. By reducing redundant data stored, the amount of information that can be stored is increased.

Celerra data deduplication overview

Celerra data deduplication combines file-level deduplication (also called “single instancing”) and file-compression technologies to provide maximum storage efficiency while minimizing the client impact on mission-critical files. Deduplication of production data should be restricted to data that is not frequently updated to avoid possible performance issues. A helpful way to understand data access frequency is by using temperature model. The following graphic shows three temperatures for data: • Hot – Data that is frequently being written and modified • Warm – Data that relatively infrequently modified • Cold – Data that is not written to frequently

For a typical file share, only 20 percent of the data is hot, or frequently written. When a Celerra file system is deduplicated, data that is not being frequently accessed is moved to a hidden store within the same file system. During this process compression and single instancing are applied to the data to provide storage efficiency gains. On a typical departmental file share this can net 40 percent space savings on the deduplicated data.

Using deduplication with VMware

Data deduplication can be turned on for any file system mounted on the Celerra. In a VMware environment it should be enabled for file shares exported by the Celerra as they will see the most benefit from the single instancing and compression method used by the Celerra. The following graphic shows how 1 TB of user data might be handled by the data deduplication engine on the Celerra.

More information on Celerra Deduplication can be found in Achieving Storage Efficiency through EMC Celerra Data Deduplication – Applied Technology at http://www.emc.com/collateral/hardware/white-papers/h6065-achieve-storage-effficiency-celerra-dedup-wp.pdf.

Celerra Virtual Provisioning

Introduction to a virtually provisioned file system

Celerra Virtual Provisioning provides a more efficient management model for utilization of storage resources. Disk space is not consumed until it is needed and it allows storage resources to grow based upon actual usage patterns versus reserved disk allocations.

Celerra Virtual Provisioning overview

Celerra Virtual Provisioning (or thin provisioning) allows the creation of a file system that is not mapped to physical disk blocks. With virtually provisioned file systems it is possible to consume only the space that is necessary to store data written to the file system. The Celerra allows the file system to grow over time through the file system auto-extension feature to accommodate additional storage demands by clients. The following graphic gives an overview of how Virtual Provisioning allows the Celerra to make more efficient use of storage. In this example the users will see a total of 30 GB space available even though only 10 GB has been allocated and only 5 GB has been consumed. As users file up their respective drives the underlying file system will expand as needed to provide additional space.

File systems can be logically sized to required capacities, and physically provisioned with less capacity, which allows the Celerra to operate with less physical spindles at a higher capacity than would otherwise be possible. The capital and operating expense savings can be significant when compared to larger, underutilized storage arrays.

Using Virtual Provisioning

Virtual Provisioning is a powerful feature in a VMware environment since it allows some level of storage virtualization. Just as ESX supports over-committing RAM to virtual machines, the Celerra can over-commit storage resources to the ESX hosts.

The Celerra has a flexible implementation of virtually provisioned file systems allowing it to virtually provision file systems, iSCSI LUNs and iSCSI snapshots of LUNs. Virtual Provisioning is extremely useful when setting up file shares for user data. Traditionally if 1,000 users needed 1 GB of storage each then 1 TB of disk space would be required, no matter how much was actually consumed by users. Using virtual provisioning 1 TB of space can be advertised using a much smaller file system on the Celerra, which allows for higher storage efficiency. The file system is grown dynamically to consume just enough storage to support the user’s requirements. Customers with Powerlink® access can see Implementing Virtual Provisioning on EMC CLARiiON and Celerra with VMware Infrastructure — Applied Technology at Home > Products > Hardware/Platforms > Celerra Family > White Papers.

CLARiiON Thin LUNs

Introduction to a thin LUN

Similar to Celerra Virtual Provisioning, CLARiiON thin LUNs allow space to be allocated more efficiently by allowing provisioning independent of the physical storage infrastructure. This also allows for over-provisioning storage. Fibre Channel thin LUNs are allocated out of a thin pool, which is a set of disks that are dedicated to virtually provisioned LUNs.

CLARiiON thin provisioning overview

Traditionally, a storage administrator needs a forecast of storage requirements to allocate storage to a certain application or host. Typically, these forecasts are inflated to hedge against additional future capacity requirements that would necessitate possible downtime to upgrade storage if more capacity is needed.

With thin provisioning, the storage administrator can virtually allocate storage so that the host reported capacity is larger than the actual allocated space on the storage system. This simplifies sizing requirements since LUN pools can be grown on the fly, without requiring downtime by simply adding disks to the thin pool. Additionally, physical storage is allocated to the server on capacity on demand from a shared storage thin LUN pool. The administrator can monitor and replenish each storage pool instead of each additional LUN, which lowers overhead.

Using CLARiiON Virtual Provisioning

VMware environments that have flexible storage requirements are the best candidates for Virtual Provisioning. Test and development environments can readily take advantage of thin provisioned LUNs. The ability to dynamically grow the thin pool allows administrators to size conservatively and only add additional storage if it will be consumed. CLARiiON Fibre Channel thin LUNs can be used in concert with linked clones in a VMware View VDI deployment to help save space in environments where capacity utilization is more important than absolute

performance of the underlying storage. The figure below shows the properties of a thin pool on the CLARiiON. The total subscribed capacity of the pool is 5040 GB and the actual user capacity is only 3210 GB for an oversubscription rate of 157 percent.

For more information on CLARiiON virtual LUNs, see the VMware ESX Server Using EMC CLARiiON Storage Systems Solutions Guide at http://www.emc.com/collateral/software/solution-overview/h2197-vmware-esx-clariion-stor-syst-ldv.pdf.

Chapter 3 - VMware Backup Options

Celerra backup technologies

Planning to fail In the IT world, failing to plan is planning to fail. There are few subjects where

that statement rings more true than in backup and recovery. Planning how to backup a VI3 infrastructure there are two time frames that need to be defined: • Recovery point objective (RPO) – This is the amount of data loss deemed

acceptable during an outage. − An RPO of 60 minutes means that in the event of a failure or outage, no

more than one hour’s worth of data is lost. • Recovery time objective (RTO) - This is the amount of time your business

can tolerate the outage of an application or service. − An RTO of 60 minutes means that in the event of an outage your

recovery plan will allow for the resumption of the service within an hour.

The graphic above shows how RPO can be affected by the backup methodology. Snapshots are typically taken hourly or daily and give RPOs measured in hours. Celerra Replicator allows for asynchronous replication and typically gives an RPO measured in minutes. Using synchronous replication technologies offered by the CLARiiON and EMC Replication Manager can give an RPO of just seconds.

Making a business decision on acceptable RTO and RPO goals is essential in planning a backup solution. Taken together, these two goals drive the type of technology to employ in doing backups and how often those backups should be run. These decisions directly affect the complexity and cost of a backup solution. Generally, the smaller the RPO/RTO the more expensive and complex the solution becomes.

Native Celerra backup options

There are three basic methods for native backup offered by the Celerra: • EMC Celerra SnapSure snapshots • EMC Celerra Replicator • EMC Celerra NDMP EMC Celerra SnapSure and Replicator are both snapshot-based solutions. As such, they both provide a fast and efficient way to take point-in-time snapshots of a production file system that can be backed up to a disk or tape library. Backups that are done this way will be crash consistent. EMC Celerra NDMP backups can offer application consistent backup images of a production file system but require the use of third-party backup applications such as EMC NetWorker® or Symantec NetBackup. These applications can temporarily stop application I/O and flush file system and application buffers to create an application consistent image for backup to disk library or tape.

Celerra native backup technologies

Celerra SnapSure

EMC Celerra SnapSure snapshots (or checkpoints) are the fastest and easiest way to protect a production file system. Creating a checkpoint immediately creates a crash consistent point-in-time view of the file system that can be backed up without creating a performance impact on the production file system.

SnapSure can concurrently maintain up to 96 Production File Systems (PFS) read-only checkpoints and 16 read-writeable checkpoints for each file system while allowing PFS applications continued access to the real-time data.

Using SnapSure for backup

SnapSure can protect a VMware environment through the use of file system checkpoints. All CIFS and NFS exports as well as iSCSI LUNs are built on top of Celerra file systems. By creating a checkpoint on the underlying file

system an administrator can instantly create a crash consistent point-in-time snapshot of the VMware datastore. In the event of file loss or data corruption, the file system can be restored to the previous view, or the checkpoint can be mounted and exported for file recovery or backup. This is a quick and easy way to protect the VMware solution. However, it should be noted this checkpoint is crash consistent and does not protect against hardware failures on the primary storage array.

For more information on Celerra SnapSure see EMC Celerra Family Technical Review starting on slide 33 http://chucksblog.emc.com/content/CelerraFamilyTech.pdf

Celerra Replicator

Celerra Replicator v2 provides a way to replicate file systems on a Celerra locally or remotely for backup or archival. When used as a local backup method Replicator can create fully realized copies (clones) of file systems on the local Celerra, which can then be mounted to a backup host for backup to disk or tape library.

Using Celerra Replicator for local backup

Celerra Replicator is traditionally positioned as a disaster recovery feature since it allows replicating file systems or iSCSI LUNs asynchronously over long distances. However, Replicator can also locally replicate file system and iSCSI LUN objects for local use as well.

A snapshot of a file system can be invalidated if the source file system is corrupted. By using Replicator to make a fully realized copy of the file system, the data is protected from a hardware failure in the production file system. This copy can also be used for test and development work and backup to tape or another disk array while not impacting the production file system. The graphic below shows the Celerra Manager screen used to create a local copy of a file system using Replicator. This is analogous to a clone of a file system. The copy of the file system can be made from any checkpoints that exist for the target file system.

For more details on Celerra Replicator, see: http://www.emc.com/products/detail/software/celerra-replicator.htm

Celerra NDMP The Network Data Management Protocol (NDMP) was created to allow NAS

devices to back up to tape devices without passing the backup data stream through the backup server itself. This allows the Celerra to communicate with backup devices without backup software loaded on the Celerra itself. A client on the network is loaded with the backup application and acts as the management host for the backup environment.

Backing up Celerra with NDMP

NDMP allows for a LAN free backup, which means the actual data being protected is not traversing the production LAN. The backup is split into two streams, the control stream and the data stream. The control stream uses the LAN only for control information. The actual data being backed up is sent over a FC link between the Celerra and a disk or tape library. This allows backups to run without impacting the production network.

NDMP traffic is offloaded from the network; this allows for dual-accessed file systems (file systems exported via CIFS and NFS concurrently) to be backed up, preserving both permission structures on the file system in the event of a restore. Implementing NDMP as a backup solution requires the use of a third-party backup software program to control the backup process. EMC NetWorker, Symantec Veritas NetBackup, CommVault Galaxy, HP OpenView, Atempo Time Navigator, and IBM Tivoli Storage Manager (TSM) all support NDMP backups. For information on using Celerra NDMP with EMC Rainfinity FMA see EMC Solutions for Rainfinity File Management Appliance EMC Celerra NS Series Solutions Guide at http://www.emc.com/collateral/solutions/solutions-guide/h5669-solutions-for-rainfinity-fma-celerra-ns-solutions-guide.pdf.

Chapter 4 - Business Continuity Features of Celerra

Enabling business continuity for VMware environments

Introduction Business continuity (BC) is the activity performed by an organization to

ensure that critical business functions will be available to customers, suppliers, regulators, and other entities that must have access to those functions. The VMware BC application is Site Recovery Manager (SRM). SRM manages and automates the processes that are required when failing over operations from a production site to a secondary site due to disasters or failures at the primary datacenter. SRM is not a replication technology that can operate by itself. SRM is tasked with managing the processes and automation steps in recovery. As such, it is dependent on other technologies to replicate data from the primary site to the secondary site. This chapter will explore how SRM leverages Celerra Replicator and SnapSure to enable site failover.

Contents This chapter contains the following topics:

Topic See Page

SRM Enabling Technologies 21

Site Recovery Manager 22

Celerra Replicator v2

Celerra Replicator

Celerra Replicator uses SnapSure to create a read-only, point-in-time copy of a source file system and asynchronously replicate that view of the file system to a read-only copy on the destination Celerra. Replicator periodically updates this copy, making it consistent with the source file system. This read-only copy can mounted back to the local Data Mover, another Data Mover in the same Celerra, or a Data Mover at a remote site for backup or disaster recovery purposes. In order for SRM to make use of a storage system a Storage Replication Adapter (SRA) must be written for that device. An SRA is provided by EMC that ensures tight integration of the Celerra Replicator v2 with VMware Site Recovery Manager. These scripts support array discovery, replicated LUN discovery, test failover, and actual failover. Currently, only iSCSI LUN replication is supported with SRM.

Using Celerra Replicator for disaster recovery

During normal operations, the primary file system is online servicing reads and writes from hosts at the production site, while the secondary copy is kept in a read-only state on the remote Celerra. All write operations on the primary file system are asynchronously transferred to the secondary Celerra, where the writes are applied to the secondary copy of the data. In the event of a disaster the replicated file system on the destination Celerra can be made writeable and mounted to hosts as the destination site so that production can continue. Due to Replicator’s asynchronous nature there are intervals when the primary and secondary copies of the data are out of synchronization. These intervals are known as time out of sync intervals as shown in the figure below. These intervals can be changed on the fly by the storage administrator to achieve desired RTO/RPO objectives.

If there is more than one DR, Site Replicator can sync a single storage object with up to four different destinations, and cascade the replication from each of the four destination objects to as many as three additional destinations. This yields a net 16 replicas per source object, while enabling each replica to be governed by its own RPO. Cascading replication is not supported with SRM.

If the source file system housing the VMware datastores becomes unavailable, the destination file system can be made read/write and mounted to ESX hosts at the remote site allowing business to continue at the remote replication site.

Site Recovery Manager

Introduction to SRM

VMware Site Recovery Manager (SRM) is a disaster recovery framework that integrates with various EMC replication software products (for example, Celerra Replicator for Celerra) to automate and control the site-to-site failover of virtual machines in the event of a disaster.

SRM overview Site Recovery Manager is an integral component of the VMware

infrastructure that is installed within a vCenter Server controlled VMware data center. SRM leverages the data replication capability of the underlying storage array to create a workflow that will fail over selected virtual machines from a “protected site” to a “recovery site” and bring the virtual machines and their associated applications back into production at the recovery site in the event of a disaster or disruption of service at the primary site. SRM recovery plans can leverage the Celerra snapshot features to non-disruptively test the failover process to ensure that the secondary image is consistent and usable. SRM relies on two independent VMware vCenter servers to be in place at both the protected (primary) site and at the recovery (secondary) site to facilitate the failover process between the two sites.

Storage Replication Adapter (SRA)

The EMC Celerra Replicator Storage Replication Adapter for VMware Site Recovery Manager is a software package that allows SRM to implement disaster recovery for VMware ESX 3.5 virtual machines using EMC Celerra network-attached storage systems running Celerra Replicator and SnapSure software. Although SRM supports FC or iSCSI LUNs, Celerra Replicator only supports iSCSI LUNs for use with SRM (as of the writing of this document).

SRM logical architecture

The figure below shows what the architecture looks like once SRM has been installed and configured to protect a VI3 infrastructure environment.

For a brief video chalk talk see EMC and VMware: The Ultimate Disaster Recovery Solution at http://www.emc.com/collateral/demos/microsites/mediaplayer-video/video-baker-tothepoint.htm

SRM failover SRM has rules to define what VMs are important and how they should be

brought up at the protection site in the event of a disaster. SRM accomplishes this by defining the following two entities: • Protection Groups are located at the protected site and define which VMs

to protect • Recovery Plans are located at the recovery site and define steps for

recovering VMs In the event of a failure at the protected site, SRM will fail over production to the protected site. As part of this event, SRM: • Automates the failover of the EMC Celerra Replicator session • Marks the protected data writeable • Fixes the LUN masking • Rescans and adds datastores • Registers and powers on VMs at the protected site These VMs become the temporary production data center as shown below.

SRM automates all the steps to restore production after the failover, which helps take error-prone manual steps out of the equation and makes for a smooth transition to the temporary production site.

SRM automated failback with the EMC Celerra Failback Plug-in

SRM does not support automated failback. Normally this means that to fail back to the production datacenter the system, network and storage administrators will have to work together to: • Shut down recovery VMs • Fail back storage • Rescan protected storage • Unregister protected VM • Rename datastore • Register protected VM • Reconfigure protected VM • Delete .vswp files • Power on protected VM • Unregister recovery VM • Rescan recovery storage EMC has authored a vCenter that will automate fail back to the production site. The EMC Celerra SRM Failback Plug-in will greatly increase the speed in which the IT staff can recover production to the original protected site.

By leveraging the EMC Celerra together with the EMC Celerra SRM Failback Plug-in, an IT staff can accomplish a failback to the original production data center much faster and with a higher degree of accuracy than would be possible if failback was executed manually.