DISASTER RECOVERY IN AN EMC DISKXTENDER FOR WINDOWS ENVIRONMENT

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1 White Paper DISASTER RECOVERY IN AN EMC DISKXTENDER FOR WINDOWS ENVIRONMENT Recommended best practices Abstract This white paper explains how to prepare for disaster recovery in an environment where EMC DiskXtender for Windows is deployed. It explains the best approaches for data replication, and also covers steps to bring an alternate site online in the event of a disaster. May 2013

2 Copyright 2013 EMC Corporation. All Rights Reserved. EMC believes the information in this publication is accurate 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. All other trademarks used herein are the property of their respective owners. Part Number h

3 Table of Contents Executive summary... 4 Audience... 4 Introduction... 4 Considerations for a DR-ready DiskXtender configuration... 5 Configuring a standby DiskXtender server... 6 Replication of extended drives... 6 Block-based replication... 6 File-based replication... 6 Replication of secondary storage... 7 Saving the DiskXtender registry configuration... 7 Configuring the License server... 7 Configuration 1: Block-based replication... 8 Setting up the primary site... 8 Setting up the alternate site... 8 Normal usage... 9 Steps to bring the alternate site online... 9 Configuration 2: File-based replication Setting up the primary site Setting up the alternate site Normal usage Steps to bring up the alternate site Configuration 3: Multi-target migration Setting up the alternate site Setting up the primary site Normal usage Steps to bring up the alternate site Summary Conclusion References

4 Executive summary In mission-critical installations, it is absolutely necessary to keep an alternative site ready to take over in case the primary site is unavailable. The alternate site should have hardware, software, and user data identical to the primary site. In EMC DiskXtender for Windows installations, the hardware includes primary and secondary storage devices, and the DiskXtender server. The software includes DiskXtender and other necessary utilities. The user data is partially on the primary storage, and partially on the secondary storage. Because of this distributed nature of data, the preparation of the alternate site is not a trivial task. The steps necessary to prepare such an alternate site are explained in this white paper. These steps often involve selecting a proper replication technique to replicate user data. The replication can be at the primary storage level, and/or at the secondary storage level. The white paper covers the possible replication techniques, and the best practices to select and configure them. The steps involved in bringing the alternate site online in the event of a disaster are also covered. Three possible configurations are covered in detail two configurations where only the primary storage is replicated; and one configuration where both the primary storage and the secondary storage are replicated. Audience This white paper is intended for DiskXtender administrators. A basic familiarity with installation and usage of the product is assumed. Introduction DiskXtender for Windows is a file archival solution from EMC. It enables users to archive less-frequently used files to low-cost secondary storage. The archived files are replaced by a stub file on primary storage. In this case, the archived data is always available for access. When the user (or any application) accesses the primary data, DiskXtender detects that access, and retrieves (or fetches ) the data seamlessly back to primary storage. DiskXtender is often used as a centralized resource, and exposes file shares where multiple users store their data. If the server is unavailable, the users experience a data unavailability event. Depending on the importance of the data, it may be necessary to prepare for such an event in advance by replicating the complete setup at an alternate site. This essentially means being prepared for a disaster. The key technology for a disaster recovery preparation is replication. Replication allows keeping the data at an alternate site in sync with the data at the primary site. There are several technologies available for replication including EMC Centera replication, MirrorView, RecoverPoint, RepliStor, and Symmetrix Remote Data Facility (SRDF ). You can replicate either the extended drives, or the secondary storage, or both. It is important to understand the advantages and limitations of each of these technologies, 4

5 before one can make preparations for disaster recovery. In this white paper, we describe the steps to devise an effective disaster recovery (DR) strategy for the data that DiskXtender manages. This white paper is organized as follows: First, we describe the important components of a typical DiskXtender installation that should be duplicated at the alternate site. Next, we describe the replication methods available for replicating extended drive data, and secondary storage data. After this, we describe three possible DR-ready configurations. For each configuration, the steps required for setting up the alternate site and the steps required to bring it online are covered. Finally, a summary of the advantages and disadvantages of each of these configurations is provided. Readers can implement any of these configurations to prepare for a disaster event. Considerations for a DR-ready DiskXtender configuration Figure 1 shows the main components of a typical DiskXtender configuration. Figure 1. Typical DiskXtender configuration While planning for an alternate site that will take over the functions of the primary site, you need to replicate each of the following components: The DiskXtender server The extended drives The secondary storage The DiskXtender registry configuration 5

6 The License server Configuring a standby DiskXtender server The alternate site should have a standby DiskXtender server configured, and it should be ready to use. It is necessary to keep the versions of the operating system and the DiskXtender software identical to the primary site. It is recommended, but not necessary, to keep the hardware identical on both sites. Replication of extended drives The DiskXtender server at the alternate site should have an identical number of extended drives as the primary site. Each extended drive on the alternate site should be equal in size or bigger than the corresponding drive on the primary site. If the two sites are within close proximity, you can use SAN-based storage so that the servers at both sites access the same LUN. This method removes the necessity of replicating the extended drives. However, it is more likely that the sites are far apart, and use separate drives. In this case, you need to use some replication method (either block-based or file-based) to replicate the extended drives. Block-based replication In case you are using SAN-based storage such as EMC Symmetrix or CLARiiON, you should use the native replication technology supplied by the SAN storage. Such replication is at a block level and does not involve the host. The data on a replicated extended drive will be identical to the data on the primary extended drive. Thus, fetched files will be replicated as fetched files, and file stubs will be replicated as stubs. Another alternative for block-based replication is to use the EMC RecoverPoint appliance. When block-based replication is being used, the DiskXtender server at the alternate site should not be active. It should be made active only as a part of the disaster recovery steps. File-based replication In case you are using local disks as primary storage on the DiskXtender server, you can use file-based replication technologies such as EMC RepliStor to replicate the extended drive. RepliStor replicates the full file data, and does not replicate the extended attributes of files. Thus, all files (including unmanaged, fetched and purged files) will be replicated as unmanaged files at the alternate site. The DiskXtender at the alternate site should archive these files again to its secondary storage. The DiskXtender Installation Guide explains the setup of RepliStor with DiskXtender. Another alternative for file-based replication is to use the multi-target migration feature in DiskXtender. The DiskXtender Administration Guide explains how to set up multitarget migration. The DiskXtender Best Practices Guide contains some important guidelines for setting up replication. 6

7 When file-based replication is being used, the DiskXtender server at the alternate site should be active. Replication of secondary storage When the extended drive is replicated with block-based replication, even the secondary storage must be replicated. The replication method for the secondary storage depends on the hardware being used. In case you are using EMC Centera as the secondary storage, you can use EMC Centera replication 1 to keep a copy of the data at the alternate site. In case you are using the EMC Atmos cloud as the secondary storage, you can enable appropriate policies on Atmos to maintain multiple replica copies of your data in the cloud. Likewise, use the native replication method for any NAS secondary storage. The alternate site should have an identical replicated storage with equal or larger capacity. You need to choose the proper replication method for secondary storage. You can use either synchronous or asynchronous replication, depending on the distance between the two sites, and the network bandwidth. Saving the DiskXtender registry configuration DiskXtender keeps important configuration information in the Windows registry. This configuration contains the media services, media, move rules, purge rules, and other important data required for the archival operation. When block-based replication is being used, before bringing the alternate site online, it is necessary to copy this registry information from the primary site to the secondary site. The DiskXtender administrator provides methods to regularly back up the registry to a network share. You should configure the DiskXtender on the primary site to store its registry on a network share. This network share should be located at the alternate site, so that it is available even after the disaster event. Configuring the License server The License server for DiskXtender is usually placed at close proximity to the DiskXtender server. But for a DR-ready configuration, it may be advantageous to keep the License server at a different location, such that it is accessible from both the primary site and the alternate site. If this is not feasible, you should keep a copy of the license file at a safe location. This copy can be used to bring a new License server online at the alternate site in the event of a disaster. DiskXtender has a grace period that is sufficient to do this. The lack of a License server will not delay your alternate site from coming online immediately. 1 DiskXtender understands EMC Centera replication, and you can specify the address of the replica EMC Centera in the DiskXtender administrator at the time of configuring the EMC Centera media service. Thus, if there is a partial failure at the primary site the DiskXtender server remains intact, but only the primary EMC Centera fails then DiskXtender can automatically connect to the replica EMC Centera and access all the archived data. 7

8 Configuration 1: Block-based replication In this configuration, we use Symmetrix 2 LUNs for extended drives. The secondary storage is EMC Centera. Symmetrix replication uses SRDF, while EMC Centera is replicated using EMC Centera replication. Steps for setting up the two sites are detailed below. Setting up the primary site 1. Install Symmetrix, EMC Centera, and DiskXtender by following the respective product guidelines. 2. Create LUNs on Symmetrix, and configure them as extended drives for the DiskXtender server. 3. Create an access profile on EMC Centera for DiskXtender, and configure an EMC Centera media service on DiskXtender using this access profile. The access profile should also have access permissions on the replica EMC Centera. 4. Configure the License server either at the primary site or at a neutral site. 5. Configure DiskXtender to save its registry configuration regularly at a server on the alternate site. 6. Configure media and policies on DiskXtender. 7. Create network shares from each extended drive that will be used by clients for file services. Setting up the alternate site 1. Install Symmetrix and EMC Centera at the alternate site by following the respective product guidelines. 2. Install DiskXtender on an alternate server but keep the DiskXtender service off. The DiskXtender server should have the same server name as the primary site server, but the IP address need not be identical 3. There is no need to create any extended drives, media services, or policy rules for DiskXtender at the alternate site. 3. Create LUNs on the Symmetrix, equal in size to the primary LUNs. Verify that the Symmetrix LUNs are accessible from the DiskXtender server. 4. Configure SRDF to replicate each of the LUNs from the primary site to the alternate site. 5. Configure EMC Centera replication. If you are using an application profile to access EMC Centera, copy the.pea file to the DiskXtender server. 2 Symmetrix is used here as an example of SAN storage. You can use other SAN storage in place of Symmetrix. 3 The requirement for keeping the server name identical is to ensure a quick disaster recovery. If it s not possible to keep the same name, you can use another name. But in such a case, you need to use the DXOTGKB utility Refer to the recovery steps. 8

9 Normal usage Clients of the file server can store their files on the network shares exposed from the extended drives. These files will physically reside on the Symmetrix LUNs. SRDF will replicate this data to the alternate site. DiskXtender will apply its archival policies to move files that match the move rules from the extended drives to EMC Centera media. EMC Centera replication will replicate the data to the replica EMC Centera at the alternate site. Files that match the DiskXtender purge rules will get purged from the extended drive. SRDF will in turn replicate the stubs to the alternate site. In case the clients delete some files, even these delete transactions will get replicated at the alternate site. Optionally, you can use EMC Centera retention to retain the files. All this time, the DiskXtender server at the alternate site will be ready but offline. Steps to bring the alternate site online In the event of a disaster, you should follow these steps to bring the alternate site online. 1. Follow SRDF procedures to break the mirror relationship for the replicated LUNs, if not broken automatically. 2. Promote the replicated LUNs so that they become read-write capable. 3. Use the Registry Log wizard to import the registry configuration from the saved location in DiskXtender. 4. Use the Change Extended Drive Serial Number Wizard to change the extended drive IDs. 5. Use the DXOTGKB utility to change the name of the DiskXtender server, if it is not the same as the primary site. 6. Turn on the DiskXtender service. 7. Verify that a few sample files are accessible. You should try both fetched as well as purged files. 8. You can keep the EMC Centera replica in read-only mode. This ensures that new data is not archived to Centera, but the archived data is accessible. 9. Enable network shares from each of the extended drives. 10. Reconfigure the network clients so that they can access the network shares from the alternate site. 11. If the License server is down, re-install it on another server, and install the license from the saved copy of the license file. This step can be done within the license grace period (14 days). 9

10 Important: You should test this procedure at least once, to make sure that you have everything in place to bring the alternate site online. Configuration 2: File-based replication In this configuration, we use local storage (disk/raid) for extended drives. The secondary storage can be EMC Centera/NAS/any other media. RepliStor is used for replicating the files on the extended drives. Steps for setting up the two sites are detailed below. Setting up the primary site 1. Install DiskXtender and RepliStor by following the respective product guidelines. 2. Configure extended drives on the DiskXtender server from the local storage. Configure the secondary storage, and the archival policies. 3. Configure the License server at the primary site. 4. Create network shares from each extended drive that will be used by clients for file services. Setting up the alternate site 1. Install DiskXtender on an alternate server. Configure extended drives from its local storage, equal in number and size to the primary server. 2. Configure secondary storage and archival policies. You can use a different class of secondary storage at the alternate site. For simplicity, use the same secondary storage and archival policies as the primary site. 3. In this configuration, the DiskXtender server at the alternate site is kept active. You need an additional License server and licenses for the alternate site. 4. Configure RepliStor to replicate files on each extended drive from the primary site to the alternate site. Normal usage Clients of the file server can store their files on the network shares exposed from the extended drives at the primary site. These files will physically reside on the local storage at the primary server. RepliStor will replicate these files to the alternate site. At each site, DiskXtender will apply its archival policies to move files that match the move rules from the extended drives to the secondary storage. Note that RepliStor replicates full file data. In case the clients delete some files, even these delete transactions will get replicated at the alternate site. Optionally, you can use EMC Centera retention to retain the files. 10

11 Steps to bring up the alternate site In the event of a disaster, you should follow these steps to bring up the alternate site. 1. Follow RepliStor procedures to break the mirror relationship for the replicated extended drives, if not broken automatically. 2. Create network shares from each of the extended drives, identical to the ones on the primary server. 3. Reconfigure the network clients so that they can access the network shares from the alternate site. Important: You should test this procedure at least once, to make sure that you have everything in place to bring the alternate site online. Configuration 3: Multi-target migration In this configuration, we use the multi-target migration feature of DiskXtender to keep an additional copy of data at the alternate site. The primary storage can be local disk or SAN. The secondary storage can be EMC Centera/NAS/any other media. Steps for setting up the two sites are detailed below. Note that the alternate site steps are given first. Setting up the alternate site 1. Install DiskXtender. Configure extended drives on the DiskXtender server from the local storage. Configure the secondary storage, and the archival policies. 2. Configure the License server at the alternate site. 3. Create network shares from each extended drive these will be used by the primary server as NAS shares. Setting up the primary site 1. Install DiskXtender on the primary server. Configure extended drives from its local storage. 2. Configure the secondary storage device at the primary site (Centera/NAS/any other media). 3. Create two media services on DiskXtender one for the local secondary storage, and another for the NAS shares exposed by the alternate site. The NAS shares at the alternate site should be created as Aggregate NAS media. 4. Configure multi-target media groups for each extended drive, such that the data is archived to both the local storage as well as the alternate site. 5. Create archival policies in DiskXtender such that all files are moved to secondary storage, irrespective of their size, age, or any other criteria. Purge rules can be set as per your choice. 11

12 6. Configure the License server at the primary site. 7. From each extended drive, create network shares that will be used by clients for file services. Normal usage Clients of the file server can store their files on the network shares exposed from the extended drives at the primary site. These files will physically reside on the local storage at the primary server. DiskXtender will archive them to the local secondary storage, and also to the network shares exposed by the alternate site. Essentially we use DiskXtender as both the archival software and the replicator in this configuration 4. Steps to bring up the alternate site In the event of a disaster, you should follow these steps to bring the alternate site online. 1. At the alternate site, create network shares from each of the extended drives, identical to the ones on the primary server. 2. Reconfigure the network clients so that they can access the network shares from the alternate site. Important: You should test this procedure at least once, to make sure that you have everything in place to bring the alternate site online. Summary The following table shows a comparison among the three recommended configurations for disaster preparedness. Table 1. Comparison of configurations Feature Configuration 1 Configuration 2 Configuration 3 Primary storage Symmetrix/ Any Any CLARiiON/ SAN Extended drive replication method SRDF/ MirrorView/ RepliStor (File-based) DiskXtender (Multi-target) RecoverPoint (Block-based) 4 One limitation of this approach is that DiskXtender does not replicate empty folders to the alternate site. 12

13 Feature Configuration 1 Configuration 2 Configuration 3 Secondary storage EMC Centera Any Any Secondary storage replication EMC Centera replication None None Primary storage capacity 2x (identical device) 2x (device can be different) 2x (device can be different) Secondary storage capacity 2x (identical device) 2x (device can be different) 2x (device can be different) License capacity 1x 2x 2x Retention capable Yes Yes Yes DiskXtender at alternate site Offline Active Active Note: EMC RepliStor is no longer sold and RepliStor v6.4 primary support ends on 30- June Configuration 1 has the advantage that it requires only one set of licenses, whereas Configurations 2 and 3 need two sets of licenses (server license and capacity license). Block-based replication is the preferred method because it puts lesser load on the DiskXtender server. One slight disadvantage with block-based replication is that even when a file is fetched or purged, it results in those changes being replicated to the alternate site. With file-based replication, data is replicated only once. Also note that Configuration 1 requires the same primary and secondary storage devices at both sites 5. Configurations 2 and 3 provide complete flexibility in terms of choosing the storage devices, but the capacities have to match. From the table, it is apparent that if you have SAN-based primary storage, and EMC Centera as secondary storage, then Configuration 1 is a preferred solution for disaster readiness. This is because of two reasons first it requires less license capacity, and second the block-based replication puts less load on the DiskXtender server. If these conditions are not met, then you can opt for either Configuration 2 or 3 to meet your disaster readiness criteria. 5 With RecoverPoint as the replication solution, they can be somewhat different but both need to be SAN devices. 13

14 Conclusion DiskXtender for Windows allows multiple methods for being prepared for disaster recovery. Depending on your requirements and storage setup, you can choose any one of the methods detailed in the white paper. References 1. EMC DiskXtender Release 6.5 Microsoft Windows Version Installation Guide 2. EMC DiskXtender Release 6.5 Microsoft Windows Version Administration Guide 3. EMC DiskXtender Release 6.5 Microsoft Windows Version Best Practices Guide 14