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[Share]Overview of migrating apps to cloud

More Posted time:Jan 16, 2017 14:08 PM
With its continuous development and popularization, cloud computing technology has generated a far-reaching impact on traditional IT system building in terms of network construction, business operation, system operation and maintenance. More and more enterprises choose to migrate their application systems to the cloud platform, and leverage the features of cloud computing platform products to build low-cost, flexible, high-performance, high-reliability, high-security IT business systems with on-demand access to computing capability.
In order to realize the migration of the existing IT system to the cloud computing platform and deployment of new systems, and to guarantee smooth migration of the system, this article mainly discusses how to migrate the offline system to Alibaba Cloud computing platform in view of the majority of enterprise system architecture components, such as the network layer, application service layer, file storage layer, and database service layer.

Network layer
The network types of Alibaba Cloud products are divided into private networks and classic networks.
Classic networks refer to that each of its independent product has public IP and private IP addresses for the convenient access of on-cloud and off-cloud customers.
An Alibaba Virtual Private Cloud (VPC) is a virtual private cloud built and customized based on Alibaba Cloud. Full logical isolation is achieved between different VPCs. You can create and manage cloud product instances, and configure route tables and gateways in your own VPC. In addition, you can establish a customized network environment by connecting the VPC and traditional data center through a private line/VPN to achieve smooth migration of applications to the cloud.
For example: migration from the traditional VLAN architecture to Alibaba Cloud VPC

The figure shows the architecture of an e-commerce website migrated to the Alibaba Cloud. This business is deployed in Shenzhen and Shanghai and the deployment architectures in the two places are identical. The specific situation is as follows:
•            One VPC is created and deployed in every region.
•            VPC is connected with the Telecom and Unicom data centers of the offline systems through the two SDH special lines.
•            There are two subnets in the VPC, one as the public network zone and one as the managerial network.
•            ECS in the VPC must be of the SSD type.
•            SLB is used as the Layer-1 load balancing for providing external access services and the Tengine established on the ECS can be used as the Layer-2 load balancing.

Application service layer
For the application service layer, you can use SLB + multiple ECS instances to replace the traditional F5 + back-end server cluster, to migrate the application service layer onto the cloud.
Server Load Balancer is a service that distributes traffic among multiple ECS instances. SLB can expand the application system's service capability through traffic distribution, and improve the system's availability by eliminating SPOF.
An ECS (Elastic Compute Service) instance is a virtual computing environment, including a CPU, memory, and other basic computing components. It is the actual operating entity presented to each user by the ECS. No advance investment is required. You can create instances, resize disks or release any ECS instances at any time as you need.
For applications of the traditional business systems deployed on the X86 physical servers or virtualized platform virtual machines, we can migrate the system applications to Alibaba Cloud through migrating application images. Alibaba Cloud currently provides P2V and V2V tools that support generating image files for most versions of Windows or Linux operating systems. Through the image import entry on the Alibaba Cloud ECS console, you can import the image files into the Alibaba Cloud image management center and then create ECS instances based on the uploaded image without the need to reinstall the system, re-establish the application infrastructure, and re-deploy the applications to migrate the application server.
Application services of the AIX, HPUNIX, and Solaris operating systems running on small machines can be migrated to Alibaba Cloud ECS instances by means of app repackaging and manual deployment. The app repackaging and manual deployment approach mainly includes basic environment installation and configuration, application middleware deployment, application code deployment and configuration. For clustered application services, after the manual deployment is completed, user-defined images can be generated through the Alibaba Cloud, and then ECS instances can be created in batch through the image to achieve cluster deployment.
By configuring the SLB, the network traffic of HTTP/HTTPS, TCP and UDP can be distributed to different ECS instances on the back end according to the polling or the minimum number of connections or the weighing policy to achieve network traffic load balancing.
For example: To achieve a wide regional distribution of users and meet the high real-time and availability needs, the key aspect of deployment is to meet the disaster recovery demands on the application service layer and achieve low-latency for users accessing the application from different regions.

Applications with users in different regions and that use lines of different carriers can use the enterprise version of the cloud resolution DNS service to direct each user to the SLB in the most suitable region and achieve cross-regional disaster recovery. A combination of SLB and ECS enables local disaster recovery for multiple zones, while the SLB health checks eliminates SPOFs.
File storage layer
For file storage migration, you can directly use OSS to replace the traditional file server or NAS storage to achieve storage of massive data files. Object Storage Service (OSS) is a cloud storage service provided by Alibaba Cloud, featuring massive capacity, security, low cost, and high reliability.
OSS is mainly applicable to the following scenarios:
•            Massive storage for image and audio/video applications
•            Static/dynamic resource separation for webpages and apps
•            Use the Media Transcoding Service (MTS) and Image Processing Service (IMG) in combination to process data on the cloud.
To migrate file storage to Alibaba Cloud OSS, a small amount of small files can easily be migrated to the OSS by uploading them through the OSS Web console. For a small number of small files or large files, you can migrate the file storage through the OSS client. OSS client supports GUI-oriented drag-and-drop operations, automatic multipart resumable upload and multi-threaded upload and other features. For a large number of files, Alibaba Cloud recommends the OSSImport2 tool for the migration. OSSImport2 is a tool for quickly migrating file data onto the cloud, the data is not stored in the disk, and multi-threaded and cluster deployment can be automatically started based on the bandwidth.
For example: file storage migration to OSS-seamless smooth migration solution

First, the client accesses the OSS directly. For the read request, if the file exists, the client returns the result and the operation is over. If the file does not exist, the redirection address according to the back-to-source redirection rule is returned. The client accesses the file in the source site according to the redirection address and returns the result. For the write request, the client writes the data to the OSS directly and returns the result. At the same time, you can configure OSSImport2 at the back end to migrate the source site files to the OSS. After the migration is completed, you can directly cancel the back-to-source rule to achieve seamless smooth migration of file storage to the OSS.
Database service layer
Big data is leading us to change from the IT era to the DT era. The “data” source is embedded in the thousands of application systems around us, such as sites, forums, ERP systems, order systems, procurement systems, and game applications. Most of application systems are on-line transaction processing systems, while the most suitable and convenient data management systems are relational databases, such as MySQL, MSSQL, Oracle and so on.
The relational database service (Relational Database Service, or RDS in short) provided by Alibaba Cloud is a stable, reliable, and auto-scaling online database service. RDS uses an out-of-the-box approach and is compatible with MySQL, SQL Server, PostgreSQL and PPAS relational databases. In addition, it provides online database resizing, backup and rollback, performance monitoring, and analysis functions. Using RDS with ECS doubles I/O performance and allows for communication via intranet, thus avoiding network bottlenecks.
Off-cloud MySQL, SQL Server, PostgreSQL, and PPAS can all find their counterparts on the RDS on Alibaba Cloud. You can establish Oracle databases on the ECS on the cloud or migrate the database to the cloud after some transformation.
Alibaba Cloud mainly uses DTS for migrating database structural data. Alibaba Cloud DTS (Data Transmission Service) supports database-centered structures and data transmission between different storage products. It integrates capabilities such as data migration, data subscription, and real-time data synchronization. You can use DTS to easily create secure, scalable and highly available data architecture.
What's supported by DTS data migration

The data migration steps of DTS mainly include:
•          Pre-check: Pre-check is a necessary stage before a migration task is started. It mainly checks the pre-conditions that may contribute to successful migration. If the pre-check fails, you can re-perform the re-check after repairing the issue.
•          Structure migration: For migration of the structured object definition syntax and structural migration between heterogeneous databases, DTS will map the data types and modestly adjust the definition syntax according to the target instance syntax definition.
•         Full data migration: It refers to migration of all the data in the source instance database, not including the definition of structure syntax, to the target instance.
•          Incremental data migration: It refers to migrate the incremental data written to the source instance during the migration process to the target instance.
    Through the introduction of the migration technologies on various layers of most of the enterprise system architecture components, users can migrate their off-line traditional IT business systems more smoothly to Alibaba Cloud leveraging these migration technical solutions. With the help of products on the Alibaba Cloud computing platform, users can enjoy values that are low-cost, elastic, high-performance, high-reliability, highly secure and with on-demand computing capabilities and achieve expected revenue.