VNXe
This chapter presents the following topics:
Protection technologies ... 70
Configure data protection ... 73
SQL Server disaster recovery ... 93
Data protection and SQL Server performance ... 95
Protection technologies
One way to protect SQL data is to use snapshot and replication features. This chapter explains what these features are and how to configure replication for a production SQL Server environment on the VNXe series.
Snapshots
A snapshot is a virtual point-in-time image of the data within a storage resource that has changed since the last snapshot. Snapshots provide a record of the content in the targeted storage resource at a particular date and time, but are not mirror copies of the data. Periodically creating snapshots of file systems and virtual devices is an effective technique to meet data protection and recovery requirements.
Note VNXe snapshots are not a substitute for storage backup operations.
Snapshots are not intended to provide resources for disaster recovery or from loss of physical equipment.
Replication
Storage replication is a process in which storage data is duplicated either locally or to a remote network device. Storage replication provides an enhanced level of
redundancy in case the main storage backup system fails. Replication minimizes the downtime-associated costs of a system failure and simplifies the disaster recovery process.
Replication produces a read-only, point-in-time copy of the source storage data and periodically updates the copy, keeping it consistent with the source data. These point-in-time copies of data are produced through snapshots.
Replication process
After a snapshot of the production environment or storage is taken, copy the snapshot to the destination array where an initial full copy occurs. When a new snapshot is taken, it is compared to the previous snapshot and only the data that has changed since the previous snapshot is copied to the destination array. This
replication process can be setup locally on a single array or remotely on another array.
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Figure 51. Replication process
Local data protection
Local replication can be used for content distribution, backup, and application testing. Local replication occurs on the same VNXe system. After communication is established, a local replication session can be set up to produce a read-only copy of the source object in a different location on the same VNXe cabinet.
Remote data protection
Remote replication can be used for content distribution, backup, application testing, and to fail over to the remote site if the primary site is unavailable. The replication occurs between a local VNXe storage server and a storage server on a remote VNXe or VNX or Celerra. To configure replication to a remote system, both the local and remote systems must be configured to communicate with one another by using a common passphrase. A passphrase is not required if both the local and remote systems are VNXe arrays.
After the communication between local and remote systems is established, set up a remote replication session to create and periodically update a source object at a remote site. After the initial copy, any changes to the local source object are
transferred to the remote destination object over the IP network. These transfers are automatic and are based on definable replication session properties.
Consistency
Consistency is the idea that some applications store critical information in more than one place. For the application to function properly, the data in each location must match or be consistent. If the data is in a consistent state, then the application can restart in the event of a failure, and come online without manual intervention. If the application data is in an inconsistent state, the application typically cannot come online automatically.
Database applications ensure consistency by not acknowledging any write until it has been successfully written to the logs. Thus, when the system recovers from a failure when the logs and the database are inconsistent, the logs are replayed on the database to restore consistency.
There are several types of consistency that dictate different recovery mechanisms and potentially different amounts of time.
Crash consistency
Data is considered crash-consistent if it will remain the same as it was before a power failure or a system outage of any kind. Because data is stored on the disk, reverting back to a specific point in time through a recovery process and resuming normal operation from that point is possible. A system ensures crash consistency by writing an I/O to disk before it commits to the application. In a scenario where there is an outage midway between the start and completion of an I/O, no data is written to disk and no acknowledgement is received by the application. When the system is up again, the data is still consistent.
Application consistency
If an application can resume normal operation from an older point-in-time copy or an image of itself without the need for any recovery calculation or process, the copy or image is said to be application consistent. Snapshots taken through EMC Replication Manager ensure application consistency. SQL Server writes all new data to the user data log. After the data is committed to the log, it is written to the user database. The user database resides on the disk and the database pages that are in active use also reside in memory. SQL Server uses a lazy writer mechanism to improve I/O
performance. Replication Manager freezes new writes and flushes dirty or unwritten transactions and database pages to the disk. The snapshot is then fractured and the database is thawed, returning to normal operation. This process ensures an
application-consistent state, and allows the snapshot to be mounted and immediately attached without having to resort to SQL Server recovery.
Data protection for Microsoft SQL Server
SQL data is essential to the smooth functioning of an organization and must be protected to ensure fast and timely recovery from site failures, planned or unplanned outages, and data corruption. SQL data on VNXe is protected by means of iSCSI replication enabled by using EMC Replication Manager.
VNXe snapshot protection provides the capability to take point-in-time consistent copies of SQL databases and revert to it in case of any data corruption. These point- in-time copies can also be utilized separately for test or backup purposes as deemed necessary in an organization.
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With the help of VNXe local replication, consistent copies of SQL databases can be copied and periodically updated on the same VNXe. In case of any data corruption, the SQL database can be re-created by restoring the databases. Local replication also creates a point-in-time copy of the most recent copy, which can be used for other business-specific operations.
With VNXe remote replication, consistent copies of SQL databases can be copied and periodically updated to a remote VNX or VNXe or Celerra. If there is any data
corruption, server failures or even complete failure of the production site, the SQL databases can be re-created by restoring the databases. Remote replication also creates a point-in-time copy of the most recent copy, which can be used for other business-specific operations.
Replication Manager
EMC Replication Manager manages EMC point-in-time replication technologies and coordinates the entire data replication process from discovery and configuration to the management of multiple disk-based replicas. It allows rapid recovery of the data on a volume to any point in time (crash-consistent recovery) or to a significant point in time (application-consistent recovery). Replication Manager allows grouping multiple LUNs as a single entity for snapshot and replication. This ensures the application is snapped and replicated in a consistent manner.
Replication Manager provides a graphical user interface to manage replication and snapshots of iSCSI LUNs. It controls the creation of snapshots, marks the snapshots for replication, and initiates the copy job from the source to the destination. During a snapshot or replication job, Replication Manager ensures that applications are in a consistent state by quiescing data reads and writes, including flushing the cache.
Configure data protection
This section describes how to configure and use Replication Manager with VNXe storage arrays to protect SQL data through replication. This document describes how to configure and replicate data between two VNXe arrays. Configuring replication on the same VNXe array is set up with the same procedure, but with some differences. These differences are explicitly mentioned in the following steps.
This section also provides information on how replicas can be used for testing, backup, or disaster recovery scenarios.
The main steps involved in the replication process are:
1. Prepare the environment for replication: Complete the following steps only once to configure replication.
a. Establish replication trust between the arrays. This step must be
performed in Unisphere. This step is not required to replicate data on the same array.
b. Install and configure Replication Manager for replication in both production and remote arrays.
2. Create and use replicas: Complete the following steps for every storage resource that is being replicated:
a. Create destination storage b. Create an application set c. Create replication jobs
3. Run and manage replication: Complete the following steps to initiate the replication process and to use the replicas created through Replication
Manager. These steps can be performed any number of times depending on the business needs.
a. Use Replication Manager to start replication b. Use Replication Manager replicas
Establish replication trust
To establish a connection between two storage platforms, complete the following steps:
1. In Unisphere, click the Hosts tab and then click Replication Connections. The Replication Connections page appears.
2. Click Add Replication Connection. The Add Replication Connection Wizard appears.
Figure 52. Replication Connections page 3. Specify the remote system details:
a. In the System Type list box, select VNXe.
Note Replication can be configured between a VNXe and a Celerra or VNX. This configuration is beyond the scope of this document. b. Select and type the network name or IP address of the remote VNXe. c. In the User Name field, type the username for the Unisphere
Management UI of the remote VNXe.
d. In the Password field, type the password to the Unisphere Management UI of the remote VNXe.
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e. In the Confirm Password field, type the password again.
Figure 53. Add Replication Connection Wizard 4. Click Next. The Summary page appears.
5. Review the details and click Finish. The results of the operation are displayed. If the operation fails in any of the steps due to any reason, failure details such as error code and error details are displayed.
6. If the storage is configured on public and private IP addresses, specify the interfaces to be used for replication. To do that, complete the following steps:
a. From the Replication Connections menu, select the destination system and click Modify. The Modify Replication Connection page appears. b. In the SP A list box, select the interface for replication on SP A. c. In the SP B list box, select the interface for replication on SP B. 7. Click OK.
Note Perform step 6 on the second VNXe as well. Ensure that each selected interface on both VNXe systems is routable from the other selected interfaces. To confirm the interfaces are routable, navigate to Settings > More Configuration > Routing Configuration to ping a particular destination IP from a specific interface.
Create replication destination storage
The replication destination can reside on the local or remote storage platform based on the replication type (remote or local). The steps to create a destination storage are the same for both types of replications (remote and local). It is assumed that the remote storage system is also a VNXe array. Replication to other EMC storage systems such as VNX and Celerra is not in the scope of this document.
To create the replication destination storage from the Generic iSCSI Storage wizard, complete the following steps:
2. Click Create a Replication Destination. The Generic Storage Wizard appears.
Figure 54. Generic iSCSI Storage page 3. Complete the following steps:
a. In the Name field, type a name for the destination storage.
b. In the Description field, type a description for the destination storage. Note The Description field is optional.
Figure 55. Specify Name
4. Click Next. The Configure Storage page appears. 5. Complete the following steps:
a. Select the pool on which the generic iSCSI storage will be created. b. In the Size field, type the size of the storage.
Note The size of the destination generic iSCSI storage should be the same as the source generic iSCSI storage that was created in Chapter 5: SQL Server Storage Provisioning. The size can be viewed in the Details page of the source generic iSCSI storage resource that is being replicated.
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Figure 56. Configure Storage page
6. Click Next. The Configure Protection page appears.
7. Select Configure protection storage, do not configure a snapshot protection schedule.
Note EMC Replication Manager that will be used to manage SQL replication has its own snapshot schedule feature. So, the Configure protection storage, protect data using snapshot schedule option must not be selected.
Figure 57. Configure protection page
8. Click Next. The Configure Protection Storage Size page appears.
9. Configure the amount of storage reserved for protection as configured on the source iSCSI storage.
Note Appendix B: iSCSI Snapshot Sizing provides more information on the space required by snapshots and how to determine an appropriate protection size.
Figure 58. Configure protection storage size page
10. Click Next. The Configure Host Access page appears with the list of currently configured hosts.
11. In the Access list box, select Virtual Disk and Snapshot for the particular host to provide host access for the mount operation. The Virtual Disk and Snapshot option provides access to all virtual disks and all promoted snapshots.
Note The host access for the virtual disk and snapshot is given to the server where the replica of the SQL Server storage will be mounted after the iSCSI copy is done. The replica must be mounted on a server to check the database consistency of the destination replica.
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Note For hosts running Windows 2008 (or later), use the quick-format option when formatting iSCSI storage resources, VMFS datastores, or Hyper-V datastores. If the full format option from Windows 2008 hosts is used and snapshot protection for the storage is enabled, then more protection storage for the storage resource must be enabled than the primary storage. If this is not done, then the snapshot operations will fail, returning an error that the protection resource is full.
12. Click Next. The Summary page appears.
13. Verify the details and then click Finish. The read-only logical disk is created as the replication destination.
Note This step must be repeated for every iSCSI storage resource that is used by the databases. For example, if you created separate storage resources for database and log files, then another replication
destination of the same size as the storage resource for logs will have to be created.
Install and configure Replication Manager
This section covers the procedure to install and configure Replication Manager, and set it up for replication.
Install Replication Manager server and agents
The prerequisites to install Replication Manager server and agents are:
• Replication Manager server must be installed on a dedicated host to manage all replication jobs.
• The Replication Manager Administration console can be installed on any host that can access the Replication Manager server.
• Replication Manager agents must be installed on all the hosts that are
currently accessing or will be accessing the storage resources in the future. To replicate SQL databases, the SQL Server agent must be installed on the host running SQL Server. Similarly, the SQL Server agent must be installed on the SQL server host at the disaster recovery site.
Note Note the port number that will be used to communicate with the Replication Manager server because that port number will be required to add the host to the Replication Manager console.
The Replication Manager Administrators Guide available on EMC Powerlink® provides more information on installing Replication Manager.
Attach hosts to Replication Manager
To attach hosts to Replication Manager, complete the following steps:
1. Start the Replication Manager console from the host on which Replication Manager Server is installed.
2. Add all hosts running the Replication Manager agents to identify the applications running on the hosts.
3. In EMC Replication Manager, right-click Hosts, and then select New Host. The Register New Host dialog box appears.
Figure 60. Adding Hosts
4. Complete the following steps:
a. In the Host Name field, type the name of the host.
For SQL data replication, this will be SQL Server that holds the databases.
b. In the Port field, type the port number.
The port number should be the number that was used when installing the Replication Manager agent on the host.
c. Click OK.
Create an application set
After successfully registering the hosts, create an application set. An application set maps and contains the data to be replicated.
To create an application set, complete the following details:
1. In EMC Replication Manager, right-click Application Sets on the left pane, and then select New Application Set. The Application Set Wizard page appears.
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Figure 61. Create an application set
2. Click Next. The Application Set Name and Objects page appears. 3. Complete the following steps:
a. In the Name field, type a unique name for the application set.
Note For SQL, Replication Manager detects the SQL Server and all the associated databases.
b. Select the SQL server host that holds the databases. The Application Credentials dialog box appears to prompt for credentials to access the SQL server.
c. Type the credentials and click OK.
Figure 62. Application Credentials
4. After verifying the credentials, all databases attached to the SQL Server are