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The editor will share with you what Windows Azure is. I hope you will get something after reading this article. Let's discuss it together.

Windows Azure is an Internet-level computing and service platform provided by Microsoft data center. Because by using Windows Azure, Microsoft maintains all the underlying operating system, hardware, network, and storage resources and constantly updates the platform, so developers and system managers no longer need to worry about the underlying software and hardware infrastructure.

Because there is a big difference between Windows Azure and intra-enterprise platforms. We strongly recommend that you test the functionality and performance of your program after you migrate it to the cloud, just as you do when you deploy it. You need to consider the following important parts when implementing the migration:

The focus of this article is Windows Azure Cloud Services. For preliminary guidance on migrating SQL Server to a Windows Azure virtual machine, see Migrating with Windows Azure Virtual Machines.

Build a verification test environment

When migrating programs to the cloud, you must know how to test and debug your programs to ensure that your programs are consistent in the cloud and locally. The following list shows the methods you can use to test your program:

Windows Azure Tools for Microsoft Visual Studio: after you create the program, you can use the computing and storage simulator to debug the program locally. This allows you to develop programs locally before publishing them to Windows Azure. Windows Azure Tools for Microsoft Visual Studio extends Visual Studio 2010 so that the additional computing and extension simulators include most of the capabilities of Windows Azure, so you can test the program locally. We recommend that you do this early in the functional test. For more information, see Windows Azure Tools for Microsoft Visual Studio.

SQL Server data tools: SQL Server Data Tools (SSDT) provides an integrated development environment in Visual Studio 2010 that you can use to design databases, create and edit database objects and data, or execute queries against all supported SQL platforms; this includes Windows Azure SQL Database in the cloud and Microsoft SQL Server 2012 in the non-cloud. This tool allows you to check the data access module in the program. Whether this part of the data is the local default database or Windows Azure SQL Database, this tool can be used to test your database project solution. For more information, see SQL Server Data Tools: note: both Windows Azure Tools for Microsoft Visual Studio and SSDT can be used to perform basic functional and compatibility tests on both online and offline data sources. But in order to really test a program running on the cloud in terms of functionality and performance scalability, you also need to test it on the Windows Azure where your program runs.

Automated testing framework: many programs already have automated testing frameworks that can be used to ensure that the modules and functions of the program work properly. Whether such automated testing frameworks can work properly when a program is running on Windows Azure depends on how such frameworks are designed. If such frameworks need to run within the enterprise but can be connected to Windows Azure through defined endpoints, they are likely to work in the cloud. Otherwise, we recommend that you migrate the automated test framework and the program itself to Windows Azure to avoid loss of connectivity and network latency.

Visual Studio load testing: if the program does not currently have an automated testing framework, we recommend that you create a new automated testing framework and use Visual Studio load tests to simulate multi-user loads. For more information, see Using Visual Studio Load Tests in Windows Azure Roles.

Synchronize the database to reduce transfer time

You should minimize the conversion time between testing, data movement, and production. Uploading internal data to Windows Azure can take hours or even days. You do not want your program to be unavailable during this time. This is why you need a plan to reduce downtime. Note that the transfer time means the time required to migrate internal programs to the final step of Windows Azure. Before moving, see which tables have the same data during the migration and which tables may change during the migration. For static data, you do not need to transfer this part of the data within the transfer time, if you are not sure whether the data in some specific tables will change within the transfer time, you should add a program in the system to migrate the changed data to the cloud. We also recommend that you consider whether all data within the enterprise needs to be migrated to the cloud in order to bring the program online on Windows Azure. If your program can come online with only part of the data in the cloud, it will greatly reduce downtime.

However, if the cloud data needs to be consistent with the internal data before the program is launched in Windows Azure, consider reducing the amount of data transferred within the transfer time. In some cases, part of the data can be transferred before the transfer time, and another part of the data can be transferred within the actual transfer time. In this case, you need to distinguish which data can be transferred ahead of time and which part of the data needs to be transferred within the transfer time. The advantage of this is that it allows your program to reduce downtime by transferring only part of the data during the online process in Windows Azure. You can use the following ways to synchronize data before the transfer time:

Windows Azure SQL Data Sync

The Windows Azure SQL data synchronization service provides the ability to synchronize data for Windows Azure SQL Databases, which currently has two main functions:

Synchronize data between SQL Server databases and Windows Azure SQL Database instances within the enterprise so that internal and cloud-based programs can use the same data.

Synchronize data between Windows Azure SQL Database instances, the synchronized instances can be in the same data center, different data centers, or even different regions.

Using the Windows Azure SQL data synchronization service to synchronize data between an enterprise internal database and an Windows Azure SQL Database instance is a good choice for the following situations:

You need to test the program in parallel.

Your program needs to continue running before migrating all the data within the enterprise to Windows Azure, and migrate this part of the changed data to Windows Azure after the migration.

Programs within your enterprise need to continue to run and reduce downtime before migrating to Windows Azure.

The program uses both cloud and enterprise internal databases as hybrid solutions.

It is worth noting that the SQL Data synchronization service uses change tracking tables to track changed tables so that these changed data are synchronized. When using the SQL data synchronization service, you must reserve space for this change tracking table. In addition, do not modify the table structure or primary key of the synchronized table unless you reinitialize the synchronization group. However, SQL Data synchronization services are not ideal in cases where mediation and real-time data synchronization are required. For more information, see SQL Data Sync. Warning: SQL Data Sync is currently only a preview version, only to collect feedback for future releases, so it should not be used in a production environment.

Replication, mirroring, transaction log shipping

You can use replication, mirroring, and transaction logs to synchronize data from one SQL Server instance within the enterprise to another SQL Server instance within the enterprise or to an instance on the Windows Azure virtual machine. However, none of these options can move data into or out of Windows Azure SQL Database. For more information, see Replication and Log ShippingandDatabase Mirroring and Log Shipping.

Custom extract, transform, load (ETL)

To reduce the time it takes to transfer data within the transfer time, you should try to transfer as much data as possible before the transfer time. You can use custom ETL job to transfer those altered data from the SQL Server within the enterprise to the Windows Azure environment. When moving data out of SQL Server versions later than 2008, we recommend using the CDC feature to ensure that only those changed data are transferred from the internal database to the Windows Azure SQL Database instance. For more information about CDC, see Track Data Changes on BOL. But for databases that do not have CDC, you need to create a data tracking system to track data that has been changed after migration. In short, migrating a minimum amount of data at the actual transfer time will greatly reduce downtime.

Export data-tier applications (DAC)

With DAC, you can export data from an SQL Server instance, store it in Windows Azure Blob storage, and later restore it to Windows Azure SQL Database. With DAC, you can set table-level filters where only the tables you need are imported or exported, but not at the row level. This is why DAC is suitable for situations where the entire table is in a separate database rather than a federated database. DAC is not suitable for programs that require real-time synchronization. For more information, see Export a Data-tier Application in BOL.

Backup and restore

Database backups are created to restore from management errors, program errors, and data loss caused by problems in the data center. Backing up and restoring data in Windows Azure SQL Database is not the same as in SQL Server within the enterprise, so it needs to be used with available resources and tools. Therefore, backup and restore Windows Azure SQL Database for reliable recovery requires a backup and restore strategy. Scenarios that require Windows Azure SQL Database for data recovery can be divided into the following three categories:

Infrastructure and hardware failures: there may be hardware failures in the data center, such as hardware nodes that provide Windows Azure SQL Database services to your data.

Problems and failures caused by programs or users: users or programs may have unexpected operations on data that need to be restored. For example, a user mistakenly modifies a customer's information, and so on.

Data center equipment damage: the current Windows Azure SQL Database service agreement specifies that reasons beyond Microsoft's control, such as problems caused by disasters, are exempt. In the event of a disaster, there may be damage to the data center where the database cannot be recovered from replication or online backup.

In the end, you need to decide the extent to which data stored in the Windows Azure SQL Database data center can be lost. "for the available backup and restore tools and the disaster recovery strategies established around them, see Business Continuity in SQL Database in MSDN."

Transfer to Windows Azure

When you really start migrating your programs to Windows Azure, you can follow these two ways:

Run in parallel: in this way, your program runs both within the enterprise and on the Windows Azure. This allows you to test the program online at Windows Azure before it runs entirely on the cloud. Your tests should include, but are not limited to: functional testing, performance testing, and scalability testing. When complete testing of the new system on Windows Azure is completed, migrate the rest of the data to the cloud and eventually shut down the system within the enterprise.

Pause and transfer: this approach applies when all data needs to be synchronized before the system goes live with Windows Azure. Using this approach requires first completing functional and performance tests on Windows Azure, and then synchronizing data to Windows Azure using the data synchronization method mentioned above. We recommend that local and cloud data be as consistent as possible to reduce the time required for final data synchronization or ETL operations. When you finally transfer to Windows Azure, shut down the system in the enterprise, do a data synchronization, and then put the program on Windows Azure online.

After reading this article, I believe you have a certain understanding of "what is Windows Azure". If you want to know more about it, you are welcome to follow the industry information channel. Thank you for reading!

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