White Paper EMC MID-RANGE STORAGE AND THE MICROSOFT SQL SERVER I/O RELIABILITY PROGRAM Abstract This white paper explains the integration of EMC Mid-range Storage arrays with the Microsoft SQL Server I/O Reliability Program. July 2011
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Table of Contents Executive summary... 4 Disclaimer... 4 Introduction... 4 EMC compliance... 5 Core 1.00 Windows logo certification... 5 Core 1.01 Windows API support... 5 Core 1.02 Stable media... 5 Core 1.03 Forced unit access (FUA) and write-through... 5 Core 1.03.01 Battery backup... 6 Core 1.03.02 Mirrored write cache... 6 Core 1.03.03 Cyclic redundancy checks... 6 Core 1.04 Asynchronous capabilities... 6 Core 1.05- Write ordering... 6 Core 1.06 Torn I/O protection... 7 Core 1.07 NTFS support... 7 Core 1.08 Testing... 7 Advanced 2.01 Write ordering... 7 Advanced 2.01.01 Local Replication... 7 Advanced 2.01.02 Remote Replication... 8 Advanced 2.01.03 Recover Point/Cluster Enabler for Windows Failover Clustering... 8 Advanced 2.02 Transactional sector/block rewrites... 8 Advanced 2.03 VDI... 8 Advanced 2.03.01 Protecting Microsoft SQL Server with RecoverPoint/SE... 9 Advanced 2.03.02 Protecting Microsoft SQL Server with RecoverPoint/SE CDP... 10 Advanced 2.03.03 Protecting Microsoft SQL Server with RecoverPoint/SE CRR... 10 Advanced 2.04 Clustering... 11 Advanced 2.05 File streams... 11 Advanced 2.06 Protection... 11 Advanced 2.07 Hardware virtualization... 11 Conclusion... 11 Appendix A: References... 12 General reference... 12 EMC customer documentation... 12 Appendix B: Microsoft I/O Reliability Specification... 12 3
Executive summary This document provides information about the compliance of the EMC mid-range storage solutions with the Microsoft SQL Server I/O Reliability Program. Information regarding the Microsoft SQL I/O reliability program is available at http://www.microsoft.com/sqlserver/en/us/solutions-technologies/mission-criticaloperations/high-availability.aspx. Disclaimer This document has been produced independently of Microsoft Corporation. Microsoft Corporation expressly disclaims responsibility for, and makes no warranty express or implied with respect to the accuracy of the contents of this document. The information contained in this document represents the current view of EMC on the issues discussed as of the date of publication. Due to changing market conditions, it should not be interpreted as a commitment on the part of EMC. Also, EMC cannot guarantee the accuracy of any information presented after the date of publication. Introduction The Microsoft SQL Server I/O Reliability Program provides a formal compliance framework and documentation for vendor solutions. EMC provides a number of highly available solutions that are covered by the Microsoft SQL Server I/O Reliability Program framework. This document provides coverage of those storage-based solutions, which are compliant under the definition of the SQL Server I/O Reliability Program. 4
EMC compliance The subsequent sections document EMC compliance with the requirements provided by SQL Server Always On documentation. The specifications applicable for the Always On program are listed under Appendix B Microsoft I/O Reliability Program. Under the program, EMC has provided compliance with the CLARiiON CX4, and VNX series storage-array products. The product name CLARiiON will be used throughout this document to denote both CLARiiON and VNX Mid-range storage arrays. Core 1.00 Windows logo certification All EMC storage platforms listed in the EMC compliance section are logo-certified by Microsoft. The Microsoft Windows Server catalog, http://www.windowsservercatalog.com/default.aspx, lists products that meet rigorous Microsoft standards for compatibility. These storage platforms are listed in the Windows Catalog under the Storage category. EMC additionally provides a solution in the Geographically Dispersed Clustering listing. The EMC RecoverPoint Cluster Enabler (RecoverPoint/CE) for Windows Failover Clustering product uses Recover Point functionality as documented within section Advanced 2.01Write ordering. Recover Point/CE for Windows Failover Clustering also complies with the Microsoft SQL Server I/O Reliability Program requirements for supported EMC storage platforms. Core 1.01 Windows API support The EMC storage arrays listed in the compliance statement fully support the core Windows API. Write operations to supported EMC storage platforms guarantee delivery to stable media as defined in subsequent sections of this document. Cache write operations are protected by battery backup systems and other cache protection mechanisms such as cache write mirroring and cache destaging to a cache vault. Core 1.02 Stable media All EMC storage arrays covered under this compliance statement fully adhere to SQL Server Write Ahead Logging (WAL) protocols and meet ACID (Atomicity, Consistency, Isolation, and Durability) requirements as defined in the SQL Server 2000 I/O Basics documentation. EMC storage arrays and replication products ensure that log predecessor writes are honored. These solutions use EMC consistency technology. Core 1.03 Forced unit access (FUA) and write-through All EMC storage arrays that comply with the Microsoft SQL Server I/O Reliability Program adhere to forced unit access and forced write-through requirements. 5
EMC storage arrays are integrated cache disk arrays (ICDA). These systems provide onboard caching that optimizes I/O operations for connected servers and associated applications. Server write operations specifically benefit from the speed of cache. Cache I/O operations are typically orders of magnitude faster than write operations to the physical disk media. All EMC storage arrays use a protection mechanism to ensure the durability and persistence of updated (write) data stored within the cache. Specifically, for storage arrays included within the I/O reliability program, a number of mechanisms are provided. Core 1.03.01 Battery backup EMC storage arrays include integrated battery backup devices. These battery backup devices are tested and certified to support the required operations in the event of a failure in the primary power supply. In the event of a primary power supply failure, cache memory is written to persistent durable media in a designated cache vault located on specific disks within the array. When primary power is restored, the cache vault is reloaded into memory, and the pending updates are submitted to the relevant logical units. Partial I/O operations are never propagated to the logical unit. Cache vault areas are implemented in a RAID configuration; therefore, the vault area is protected against disk failures. Core 1.03.02 Mirrored write cache To protect against single points of failure in the cache subsystem itself, EMC implements write cache mirroring protection. Under this scheme, updated cache areas are implemented in a RAID 1 configuration. As a result, updates are fully redundant and are protected against a single point of failure such as a memory board fault. Core 1.03.03 Cyclic redundancy checks Cyclic redundancy checks (CRC) within the array fully protect all update operations written to cache. This ensures protection against undetected faults within the array, such as intermittent data path errors. Data must pass CRC tests before the array successfully services read operations. Core 1.04 Asynchronous capabilities All EMC storage arrays that comply with the Microsoft SQL Server I/O Reliability Program meet the Asynchronous capabilities requirement. EMC storage platforms will not transition asynchronous I/O operations from a host into synchronous operations. Core 1.05- Write ordering All EMC storage arrays that comply with the Microsoft SQL Server I/O Reliability Program meet and can enforce write ordering. 6
Core 1.06 Torn I/O protection All EMC storage arrays that comply with the SQL Server I/O Reliability requirements support the Core torn I/O protection requirement. Core 1.07 NTFS support All EMC storage arrays that comply with the SQL Server I/O Reliability Program provide full support for all NTFS capabilities. Core 1.08 Testing The SQLIOSim.exe tool was executed for a required 24-hour testing cycle. SQLIOSim data durability and integrity tests are run with following configuration: CLARiiON CX4-240 o 5 200GB EFD drives o 10 600GB SAS drives All other required testing was completed using: VNX 5500 o SATA Flash storage pool o 15 184GB EFD drives All required testing was successfully completed. Advanced 2.01 Write ordering Advanced 2.01.01 Local Replication In the case of local replication, CLARiiON storage arrays under this compliance statement honor the write dependency. Write ordering in this style of configuration is managed by SQL Server, and durability of I/O operations to stable media in each array is protected by compliance to Core 1.02: Stable media. Additionally, CLARiiON storage arrays provide support for EMC consistency technology to further extend protection of write order dependency. The CLARiiON consistency technology includes support for SnapView consistent snapshot sessions and consistent fracture of clones. EMC consistency technology enables storage arrays to adhere to dependent write principles, which are the foundation of write ordering. Consistency groups can define related storage LUNs that need to be treated in an atomic manner to ensure that write ordering is protected. CLARiiON storage arrays implement consistency technology such that it internally maintains write ordering for operations such as CLARiiON SnapView consistent split operations. Figure 1 illustrates SnapView snapshots and clones using consistency technology within the same array. The resulting consistent snapshot or clone presented to the target host represents a restartable image, and complies with the I/O Reliability requirements. 7
Figure 1 EMC SnapView snapshots and clones with consistency technology Advanced 2.01.02 Remote Replication For CLARiiON storage solutions in replicated environments, RecoverPoint provides consistent write-ordered protection over long distances. RecoverPoint achieves write-order consistency for remotely replicated data by tagging each asynchronously replicated write, enabling the writes to be reassembled into the correct order at the remote site. This enables RecoverPoint/SE to provide synchronous levels of protection with no application degradation and no distance limitations. This unique capability shatters today s distance/latency limitations, and enables completely up-to-date protection from regional disasters with no impact on application performance. For synchronous remotely replicated data, the writes are sent in order so that they are received and assembled at the remote site in the same order as they were generated at the production site. Advanced 2.01.03 Recover Point/Cluster Enabler for Windows Failover Clustering EMC RecoverPoint/Cluster Enabler (CE) is a software package that enables geographically dispersed Microsoft Failover Clusters to replicate their data using RecoverPoint/SE continuous remote replication (CRR). Geographically dispersed clusters offer increased levels of high availability, disaster recovery, and automation over non-clustered solutions. RecoverPoint/CE works seamlessly with applications designed to take advantage of Failover Clusters, such as SQL Server in Microsoft Windows 2003 and 2008 environments. Advanced 2.02 Transactional sector/block rewrites All EMC storage arrays that comply with the SQL Server I/O Reliability Program fully adhere to the transactional sector or block rewrite I/O reliability requirement. Advanced 2.03 VDI All EMC storage arrays that comply with the SQL Server I/O Reliability Program fully adhere to the SQL Server Virtual Backup Device Interface (VDI) Specification. SQL 8
Server VDI integration is provided by RecoverPoint/SE, EMC Replication Manager (RM) and the EMC NetWorker Module for SQL Server. Advanced 2.03.01 Protecting Microsoft SQL Server with RecoverPoint/SE Database recovery is a major requirement that all database management systems must address and Microsoft SQL Server is no exception. Microsoft SQL Server supports crash recovery, as well as database backup and restore through a Virtual Device Interface (VDI). In most cases, recovering from a local or remote RecoverPoint image at an arbitrary point in time is a simple and straightforward process. Nevertheless, Microsoft will not support the recovery of SQL Server from arbitrary images that were not created though a supported Microsoft API. When RecoverPoint utilizes the VDI APIs to protect the SQL Server environment, Microsoft will guarantee that SQL Server will be able to recover from an application-consistent VDI image. Using the VDI APIs, RecoverPoint/SE will put SQL Server briefly into a quiescent state, which will commit in-memory transactions and then halt all writes to the database and log files. This allows RecoverPoint/SE to create a bookmark that records this image as an application-consistent VDI image. RecoverPoint/SE also captures the metadata information provided by the VDI API, which can be used later when restoring the SQL Server database. The built-in crash recovery mechanism of SQL Server allows it to recover from a power outage, hardware crash, or software crash. During crash recovery, SQL Server recovers all completed transactions while removing all incomplete transactions, thereby maintaining transactional consistency. As a result, crash recovery allows SQL Server to recover from a point-in-time image. Microsoft SQL Server manages one or more user databases. Additionally, special system databases are also used for systems configuration information. A database is composed of multiple files such as data files and log files. These files usually reside on several different volumes, all of which must be protected and restored as a single group. Protection by EMC RecoverPoint/SE is based on a logical entity called a consistency group. A consistency group is a collection of volumes managed by RecoverPoint/SE for local protection or remote replication to a target group of volumes. Within a consistency group, RecoverPoint/SE enforces write-order fidelity for the local and remote replication processes and ensures that replica volumes remain in a consistent state with respect to each other. For Microsoft SQL Server, all of the volumes for a database to be protected with RecoverPoint/SE must reside in the same consistency group. If multiple databases are to be protected, these can either reside in the same consistency group, or can be placed into a different consistency group. 9
Advanced 2.03.02 Protecting Microsoft SQL Server with RecoverPoint/SE CDP RecoverPoint/SE synchronous continuous data protection (CDP) can be used to provide any-point-in-time recovery of a stand-alone or clustered production Microsoft SQL Server environment with one or more database instances. A standalone Microsoft SQL Server can also be used as the recovery server. The production Microsoft SQL Server configuration should follow the EMC best practice storage configurations with the databases and logs on separate volumes. The RecoverPoint/SE splitter driver in the CLARiiON array will intercept all write activity to the protected volumes, and will send a copy of the write to RecoverPoint/SE, which will store it in the local CDP journal and synchronously write it to a local replica volume. When recovery is required, the user selects an appropriate image, which is either the latest image, an image with an application-specific bookmark, or an image from a specific point in time. When the user selects an image, any new writes to the production volumes are paused as the volumes are rolled back to that specific time point. This rollback operation, called instant recovery, results in an exact image consistent at the specific point in time selected by the user. Even though distribution of writes to the replica volumes has been paused, they continue to be stored in the RecoverPoint/SE CDP journal. These recovery volumes are then mounted to the recovery SQL Server, and the databases are attached using the SQL Server Enterprise Manager. If crash recovery is necessary, this will be performed by the recovery SQL Server at this time. If the user selected an image using an application-consistent VDI bookmark, then crash recovery would not be necessary, and instead Microsoft SQL Server would recognize the image as a VDI created image. At this point, the user can perform read/write operations against the point-in-time image. When the user is done with the recovered image, the database would be detached, and the volumes dismounted from the recovery SQL Server host and write distribution would be resumed to the recovery volumes. Advanced 2.03.03 Protecting Microsoft SQL Server with RecoverPoint/SE CRR RecoverPoint/SE continuous remote replication (CRR) is used between a CLARiiON array in the primary data center and a CLARiiON array at a remote disaster recovery site. Continuous remote replication is used to maintain copies of all of the volumes associated with each of the nodes in the SQL Server cluster. This also includes the server boot volumes, which are also stored on the SAN. To fully protect the Microsoft SQL Server environment, RecoverPoint/SE consistency groups are created for all database instances. Additionally, if the servers are configured to boot from a SAN-attached volume, then the boot from SAN volumes would be contained in an additional consistency group. For replication and disaster recovery purposes, the RPO policies are set on the database consistency groups to ensure that frequent small images are replicated to the recovery site. The small RPO ensures that minimal crash recovery will have to be performed at the remote site in the event of a local disaster. 10
The RecoverPoint/SE CLARiiON splitter driver intercepts the writes to the protected volumes and sends a copy of the write to the local RecoverPoint appliance. The appliance combines this write with earlier writes. If the RPO policy threshold for image size has been met, it will compress all of the writes and send it across the IP link to the remote RecoverPoint appliance. At the remote site, RecoverPoint/SE will un-compress and write the snapshot to the appropriate RecoverPoint/SE CRR journal. The writes will also be distributed to the appropriate replica volumes in the same order as they were written on the production side. This ensures that the replica volumes contain the latest possible data from the production side with write-order consistency maintained. Advanced 2.04 Clustering All EMC storage arrays that comply with the SQL Server I/O Reliability Program are qualified under Windows Server Catalog. Exclusive to Windows Server 2008, CLARiiON arrays are part of the Failover Cluster Configuration Program. Advanced 2.05 File streams All EMC storage arrays that comply with the SQL Server I/O Reliability Program fully adhere to the file streams requirement. Advanced 2.06 Protection All EMC storage arrays that comply with the SQL Server I/O Reliability Program fully adhere to the protection recommended requirement. Advanced 2.07 Hardware virtualization All EMC storage arrays that comply with the SQL Server I/O Reliability Program fully adhere to the hardware virtualization requirement. The array itself is certified under both the Windows Server 2008 and Windows Server 2008 R2 hardware logo programs. Conclusion This paper detailed the adherence of EMC CLARiiON storage arrays to the Microsoft SQL Server I/O reliability program. The I/O reliability program allows EMC to highlight CLARiiON features designed to protect data. The requirements are designed to ensure data integrity even in the event of failure. The I/O reliability program divides testing into core and advanced features. The core features included rigorous SQLIOSim testing. The EMC CLARiiON arrays meet the entire core and advanced requirements set forth by the Microsoft SQL Server I/O reliability program. 11
Appendix A: References General reference Information about running Microsoft SQL Server on EMC storage platforms is provided through the Microsoft SQL Server on EMC Symmetrix Storage Systems Techbook; http://www.emc.com/collateral/software/solution-overview/h2203-mssql-svr-symm-ldv.pdf EMC customer documentation EMC provides documentation to existing customers through the EMC Powerlink site; http://powerlink.emc.com. Appendix B: Microsoft I/O Reliability Specification The Microsoft I/O Reliability Specification is available at: http://download. Microsoft.com/download/6/E/8/6E882A06-B71B-4642-9EB4- D1EA0D6223C8/SQL%20Server%20IO%20Reliability%20Program%20Requirements %20Document.docx 12