nondisruptive storage relocation: planned events … storage relocation: planned events with emc...

Nondisruptive Storage Relocation: Planned Events with EMC VPLEX

Best Practices Planning

Abstract

This white paper covers best practices for using EMC® VPLEX™ to migrate block storage data, for purposes of a tech refresh or lease rollover, or for ongoing data mobility as performance and availability requirements change.

May 2010

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Part Number h7065

Nondisruptive Storage Relocation: Planned Events with EMC VPLEX Best Practices Planning 2

Table of Contents Executive summary ............................................................................................4

Data migration challenge ............................................................................................................. 4 Introduction.........................................................................................................5

Audience ...................................................................................................................................... 5 Technology refresh.............................................................................................5

EMC VPLEX................................................................................................................................. 6 EMC VPLEX clustering architecture ........................................................................................ 7

EMC VPLEX-assisted data relocation .............................................................10 Data migration operation............................................................................................................ 10 Post-migration considerations.................................................................................................... 15

Other considerations........................................................................................16 Conclusion ........................................................................................................17 References ........................................................................................................17


Executive summary Customers have been demanding ever-increasing service levels while looking for reduction in capital and operating costs. Data centers undergo continuous technology transformation in order to meet these changing requirements. In recent years, consolidation of server and storage resources has proven to be instrumental in reducing costs, improving utilization, and providing greater flexibility. The challenge is to leverage new technologies, while at the same time not compromise the level of service to the end users.

A cloud analogy is often used to represent the vision for a fluid and dynamic IT infrastructures. One definition of a cloud is the disassociation of IT services provided to users from the physical infrastructure. An instantiation of a cloud is where servers are virtualized and services are optimized on any server in the environment, connected to the appropriate storage, accessed from anywhere within the IT infrastructure. Additionally, the cloud analogy describes an environment where services may be seamlessly relocated as requirements change. Figure 1 illustrates a private cloud infrastructure where users and the services provided by IT are loosely coupled and the relationships between services, compute, and storage are dynamic and flexible.

Figure 1. IT services provided by any server, connected to any storage, anywhere The technology exists today to build a cloud-like IT infrastructure. EMC, the industry leader in enterprise storage, recently released EMC® VPLEX™, a solution that delivers local and distributed storage federation, allowing full read and write LUN access and transparent movement of data within the data center and between data centers. In addition, VPLEX’s storage federation allows for the seamless integration of new technologies such as the Symmetrix® VMAX™ with Enginuity™ or CLARiiON® storage arrays while critical applications continue to provide uncompromised levels of service to users.

Data migration challenge Ask any storage professional for a list of their biggest challenges and data migration will be at, or near, the top of the list. Often, data migration is required during technology refresh initiatives where newer storage systems such as the Symmetrix VMAX replace legacy storage.


Data relocation may also be required to move data between storage tiers that reside on different storage systems as performance and availability requirements change. During the information lifespan, data may have different value to the organization, and changes in availability and performance may require data movement up or down tiers. For example, when an application is in development, performance and availability may not be nearly as critical as they are when in full production, therefore development and test environments can leverage more cost-effective storage. When an application moves into production, data availability and performance increase, and likely require data movement to a higher tier. As production ramps up, even higher service levels may be required and thus some or all of the data may require the highest-performance storage, such as what Enterprise Flash Drives deliver. If this ultra-high performance storage is within the same storage system, capabilities such as Virtual LUN technologies may be leveraged to seamlessly move data within the array. If this ultra-high performance storage is located in a different storage system, data migration between systems is required.

Many different tools are available to simplify data movement between storage systems. Some are host-based such as EMC Open Replicator or PPME Copy, or are capabilities built into host Logical Volume Managers. While these tools are appropriate in some instances, they do use host resources and require the involvement of server and application administrators. Others tools are array-based such as SAN Copy™ and Open Migrator. EMC VPLEX offers a third option that is SAN-based, where data can nondisruptively move between arrays without the direct involvement of the host or the storage system.

Introduction This white paper discusses the best practices for using EMC VPLEX to nondisruptively move data for purposes of a technology refresh or lease rollover, or to do ongoing data relocation as part of normal operations and data lifecycle management.

Audience This white paper is intended for storage architects and administrators who are responsible for planning and implementing the EMC VPLEX for the purpose of data mobility and migration as part of a technology refresh. The audience has general knowledge and experience working with:

• EMC CLARiiON and Symmetrix storage systems

• Fibre Channel SAN design and operations

• VPLEX concepts and use of the CLI for basic management

Technology refresh Many data centers have a process referred to as evergreening where hardware and software resources are periodically replaced. However, this is not simply a practice of replacing the old with new. Capabilities exist today that were not available four years ago, the typical time for technology replacement. Today we have storage capabilities such as ultra-high performance storage provided by Enterprise Flash Drives, low-cost storage provided by high-capacity SATA drives, efficiency techniques such as Virtual Provisioning™, and the ability to set policies that move data between types as business requirements and workloads change. Leveraging these capabilities allows us to offer the highest service levels for our demanding clients, and to do so at the lowest possible capital and operating costs. Furthermore, data centers need to position themselves to rapidly respond to the changes in business requirements and technology development cycles, which are now measured in months rather than in years.

Virtualization of servers and federation of storage resources have proven instrumental to achieving these goals. Inserting a virtualization layer between the operating systems and server hardware, as with VMware vSphere, provides proven value in managing compute resources and changing service levels. Similarly, storage federation provides a layer between the server and storage that enables movement of data between the underlying storage systems, completely transparent to the host environment. EMC has recently released the next-generation storage federation, the EMC VPLEX, that delivers local and distributed


federation. This federation layer enables seamless migration between storage systems and allows storage administrators to leverage new storage capabilities that provide greater levels of efficiency and lower cost, without compromising service levels to end users.

EMC VPLEX The EMC VPLEX family is the next-generation solution for information mobility and access within, across, and between data centers. It is the first platform in the world that delivers both local and distributed federation.

Local federation provides the transparent cooperation of physical elements within a site. Distributed federation extends access between two locations across distance. VPLEX is a solution for federating both EMC and non-EMC storage.

EMC VPLEX introduces a new architecture, which incorporates learnings from EMC’s 20-plus years of expertise in designing, implementing, and perfecting enterprise-class intelligent cache and distributed data protection solutions.

Built on a foundation of scalable and highly available processor engines, EMC VPLEX is designed to seamlessly scale from small to large configurations. VPLEX resides between the servers and heterogeneous storage assets and uses a unique clustering architecture that allows servers at multiple data centers to have read/write access to shared block storage devices. Unique characteristics of this new architecture include:

• Scale-out clustering hardware that lets you 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 • A 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 2. Capability of the EMC VPLEX system to federate heterogeneous storage

AccessAnywhere™, available with VPLEX, is EMC’s breakthrough technology that enables a single copy of data to be shared, accessed, and relocated over distance. EMC GeoSynchrony™ is the VPLEX operating system.

VPLEX family consists of two products: VPLEX Local and VPLEX Metro. • VPLEX Local provides simplified management and nondisruptive data mobility across heterogeneous

arrays.


• VPLEX Metro provides data access and mobility between two VPLEX clusters within synchronous

distances.

Figure 3. EMC VPLEX family offering with architectural limits

With a unique scale-up and scale-out architecture, VPLEX's advanced data caching and distributed cache coherency provide workload resiliency, automatic sharing, and balancing and failover of storage domains, and enables both local and remote data access with predictable service levels.

VPLEX Local supports local federation today. VPLEX Metro delivers distributed federation capabilities and extends access between two locations at synchronous distances. VPLEX Metro leverages AccessAnywhere to enable a single copy of data to be shared, accessed, and relocated over distance.

The combination of a virtualized data center and EMC VPLEX provides customers entirely new ways to solve IT problems and introduce new models of computing. Specifically, customers can:

• Move virtualized applications across data centers • Enable workload balancing and relocation across sites • Aggregate data centers and deliver IT services “24 x forever”

EMC VPLEX clustering architecture VPLEX uses a unique clustering architecture to help customers remove the physical boundaries of the data center and allow servers at multiple data centers to have read/write access to shared block storage devices.

A VPLEX Local configuration is defined by up to four VPLEX Engines, which are integrated into a single cluster image through their fully redundant inter-engine fabric interconnections. This cluster interconnect functionality allows for the online addition of VPLEX Engines, providing the exceptional scalability for both VPLEX Local and VPLEX Metro configurations. All connectivity between VPLEX cluster nodes and across VPLEX Metro configurations is fully redundant, ensuring protection against single points of failure.

A VPLEX Cluster can scale up through the addition of more engines, and scale out by connecting clusters into a Metro-Plex (two VPLEX Metro clusters connected within metro distances). VPLEX Metro helps transparently move and share workloads, including virtualized hosts, consolidates data centers, and optimizes resource utilization across data centers. In addition, it provides nondisruptive data mobility, heterogeneous storage management, and improved application availability. VPLEX Metro supports up to two clusters, which can be in the same data center at two different sites within synchronous distances (approximately up to 60 miles or 100 kilometers apart).

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Figure 4. Local and distributed federation with EMC VPLEX Local and VPLEX Metro

EMC VPLEX maintains customer expectations for high-end storage in terms of availability. High-end availability is more than just redundancy; it means nondisruptive operations and upgrades, and being “always online.” EMC VPLEX provides:

• AccessAnywhere, with full connectivity of resources across clusters and Metro-Plex configurations • Data mobility and migration options across heterogeneous storage arrays • The power to maintain service levels and functionality as consolidation grows • Simplified control for provisioning in complex environments • Dynamic load balancing of data between storage array assets

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

• Two directors, which run the GeoSynchrony software and connect to storage, hosts, and other directors in the cluster with Fibre Channel and gigabit Ethernet connections

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

• Two management modules, which contain interfaces for remote management of a VPLEX Engine

Each cluster also consists of:

• A management server, which manages the cluster and provides an interface from a remote management station

• 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 Logically, VPLEX is similar to other storage systems, with front-end ports that connect to host and back-end ports that connect to storage systems. Storage presented to the back end is provisioned to hosts through the front end. Advanced provisioning options allow devices to be striped, mirrored, and concatenated as required by the host and application environment. The following figure and terms illustrate the configuration objects used in configuring a VPLEX and the relationships between them.


• Storage volumes: A storage volume is a device or LUN on an attached storage system that is visible to

the VPLEX. The available capacity on a storage volume is used to create extents, devices, and virtual volumes.

• Extent: An extent is any subset (including all) of the capacity on a storage volume. • Device: Devices are configured from one or more extents in a RAID 1, RAID 0, or concatenated

(RAID-C) configuration. • Virtual volume: Virtual volumes are devices that can be provisioned to a host. • VPLEX ports: VPLEX ports are front-end ports used by a host to access virtual volumes. Ports are

added when a storage view is created to define the connection between initiators and virtual volumes. • Registered initiator: A registered initiator is a host bus adapter (HBA) that has been identified on the

VPLEX. • Storage view: A storage view is a logical grouping of ports, initiators, and virtual volumes for LUN

mapping and masking purposes. A storage view is similar to storage groups used on the CLARiiON and to masking views used in Symmetrix VMAX.

Figure 5. VPLEX configuration objects

When a VPLEX is added between servers and storage systems, existing data volumes are encapsulated while preserving all prior data. When using the VPLEX for migration during a technology refresh, source and target storage volumes are presented to the VPLEX and a migration session is created. The actual data movement is from the source array, through the VPLEX to the target array, completely transparent to attached servers. The source and target devices can be of different RAID protection types and storage tiers, and may consist of EMC and non-EMC storage arrays. In addition, the target device can be larger in capacity than the source device, allowing changes in volume sizes as part of the migration. VPLEX supports data movement within the data center or between local and remote data centers when the VPLEX is configured as a Metro-Plex environment. In a multi-cluster configuration, the VPLEX can present the same volume to hosts at both the local and remote sites while maintaining write order fidelity and cache


coherency. This allows the movement of not only the storage but also the compute resources between data centers.

The VPLEX offers many capabilities, including advanced provisioning, that allow volumes to divided and aggregated to provide appropriate capacity and performance. Migrations are seldom a one-time event. With the VPLEX as an integral part of the IT infrastructure, data movement between tiers and between data centers as business and workload requirements change is seamless.

The management interface for the VPLEX includes a robust CLI and an intuitive web-based graphical user interface.

EMC VPLEX-assisted data relocation With EMC VPLEX, storage presented to hosts can be nondisruptively moved to different storage tiers within and between back-end storage arrays. To illustrate the process, an example will be used where the source volumes for the migration reside on a Symmetrix storage system, and the target volumes reside on a CLARiiON CX array. The host environment consists of a pair of ESX servers in a cluster configuration. Figure 6 shows the environment used in this example.

Figure 6. VPLEX migration scenario

For this example, the VPLEX system is installed, configured, and connected to both the Symmetrix and CLARiiON arrays. The ESX servers and both storage systems are connected to the Fibre Channel fabric as indicated above. While the scenario used to illustrate the process is based on an ESX environment, a similar process would be followed for other host environments.

Data migration operation For this example, we will initiate the migration of the data on the source devices that reside on the Symmetrix to the target devices on the CLARiiON. The migration operation is transparent to the ESX servers and the virtual machines that reside on the datastores.


The actual data movement from source to target is performed in the following manner:

• Convert the source volume from a RAID 0 to a RAID 1 configuration • Add the target device as a mirror • Synchronize the mirror • When fully synchronized, promote the target device to be the primary copy • Remove the source device to convert it back to a RAID 0 configuration

This procedure may be performed manually; however, the best practice is to use the batch migration procedure that automates the steps.

1. On the VPLEX console, create a batch migration plan. A plan is a file that identifies the source and target devices and other attributes. When the session is created, it is assigned a session name. A session can be created manually by creating and editing the plan file; however, for this example we will use the following command to create the plan file automatically. Note in this example, the wildcard character “*” was used to specify the source and target devices. cd /clusters/cluster-2/devices batch-migrate create-plan –f Datastore* -t Target_Dev* /tmp/batch_mig_plan The following is an example of the command dialog.

View the file created by the above command. This file defines the migration session details and is used by subsequent commands. In a root window on the SMS console, execute the following command. vi /tmp/batch_mig_plan The following is an example of the file that was created.

2. Check the plan and then start the migration session. The check-plan command validates the migration plan. Starting the migration will convert the source device to a RAID 1 device, add the target device as a mirror, and start the synchronization process. batch-migrate check-plan /tmp/batch_mig_plan


batch-migrate start /tmp/batch_mig_plan The following is an example of the command dialog.

3. Verify the status of the migration. The following command will show the status of all active device migration sessions. cd /data-migrations/device-migrations ll The following is an example of the dialog. Here we see the migration is in progress and 7 percent complete.

Display the device configuration. You will see that the migration process converts the source device to a RAID 1 configuration and adds the target as a mirror. Use the following command to view the configuration of the device. Note the source devices are renamed MIGRATE_<Session name>. Also, note the status of the device shows a degraded state during synchronization. This is normal until the mirror is fully synchronized. cd clusters/cluster-2/devices ll The following is an example of the command dialog.

Determine how long the migration will take. Execute the following command to display details about the source device that was renamed MIGRATE_BR0_0.


cd /cluster/cluster-2/devices/MIGRATE_BR0_0 ll

4. Verify that the migration has completed. When the migration completes the PercentageDone will show 100. Execute the following command. cd /data-migrations/device-migrations ll The following is an example of what you will see when the synchronization is complete.

Display details about the operational state of the device. It should now show OK, indicating that the RAID 1 mirrors are synchronized. cd /clusters/cluster-2/devices ll The following is an example of what you would see when the mirrors have completed synchronization.

5. Once the synchronization completes, the migration session can be committed. The following command will commit the migration.


batch-migrate commit /tmp/batch_mig

After committing, both the source and target devices are now visible with the target device being associated with the virtual volume that is presented to the ESX cluster.

Also note the migration session will show as committed. cd /data-migrations/device-migrations ll

6. The next step of the batch migration is the clean. This dismantles the source device down to the storage volume and the source storage device is changed to an unclaimed state. Using the rename option will cause the target volume to assume the name of the source volume. The following command will clean up the migration. batch-migrate clean –-rename-targets /tmp/batch_mig In the following example note that the migration target device assumed the name of the source device and it is now associated with the virtual device. Also note that the source device was removed.

Verify the source device is now “unclaimed”.


cd /clusters/cluster-2/storage-elements/storage-volumes ll

7. The final step of the batch migration is to remove all information about the migration session from the VPLEX. The following command will remove all information about the completed migration session from the VPLEX. batch-migrate remove /tmp/batch_mig The following is an example of the command dialog. Note that the session information is now gone.

Best Practice: Schedule data migration during off-hours to minimize the impact of an increased workload on the back end. Best Practice: Stop the migration during hours of production and resume during off-hours. The data migration is now complete. The final step is post-migration considerations.

Post-migration considerations If the source storage system will no longer be part of the VPLEX environment, it can be removed by performing the necessary masking, zoning, and other configuration changes. If the source devices will be redeployed for other uses in the VPLEX environment, the following steps will not be necessary.

1. On a management server connected to the source Symmetrix, execute the following commands to remove the masking view and associated initiator and storage groups for the source devices.


symaccess –sid <98> delete view –name zephyr32 –unmap symaccess –sid <98> delete –name zephyr32 –type storage symaccess –sid <98> delete –name zephyr32 –type initiator

2. Remove the zones that define the connection between the source Symmetrix and the VPLEX from the zone configuration.

3. Remove the devices from the VPLEX configuration. Use the following command to remove the source devices form the configuration. cd /clusters/cluster-2/storage-volumes storage-volume forget

To prevent access to data the source device may be deleted on the source storage array. Optionally the Symmetrix Secure Erasure Service may be used to thoroughly cleanse the data from the array.

Other considerations Up to 25 migration sessions can run concurrently on a VPLEX system. Additional sessions can be defined and queued for execution. When a session completes, a queued session will begin. Best Practice: Migrate one server or cluster at a time. Performance impacts during migration and the time it takes for a migration to complete are highly dependent on workload during the migration, storage back-end configuration, and SAN and WAN link configurations. One consideration for performance is the transfer size. The default value is 2 MB but is configurable for 4 KB to 32 MB. The transfer size defines the size of a region on the source device that is temporarily locked, read, and then written to the target. When the transfer size is set large, migration will be faster but potentially could impact performance on the front end, especially when migrating across clusters in a Metro-Plex configuration. Smaller transfer size will result in less front-end impact but migrations will take longer. Best Practice: Schedule migrations during periods of light workloads.


Conclusion Changing requirements is inevitable in all data centers. The EMC VPLEX provides capabilities not previously available by adding a storage federation layer between the server and storage systems. Federation enables nondisruptive data relocation between arrays as capacity and performance requirements change, and allows you to seamlessly integrate new storage technology meet stringent service level requirements. The migration procedures outlined in this paper used a VMware vSphere environment with Symmetrix VMAX as the source array and a CLARiiON CX3-20 as the target array. However, as can be clearly seen, while the details of the specific commands executed may change (depending on the environment), the same process can be used with other combinations of host environments and source and target arrays.

References For more specific information, reference the following on Powerlink:

• EMC VPLEX CLI Guide

• Implementation and Planning Best Practices for EMC VPLEX Technical Notes


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