Translation (15)-----to Level 1 staircase: What is SQL Server AlwaysOn

access to Level 1 stairs: What issql Server AlwaysOn

Perry Whittle,2016/02/24(first published:2014/09/24)

The series

This article is part of the series: Stair Stairs AlwaysOn

AlwaysOn is a complex set of technologies that are often misunderstood. On this staircase you will learn about AlwaysOn Technology, how they adapt to the highly available stacks, and how to use them well.

Welcome to SQL Server AlwaysOnin the first level ladder series. In this 1 -level article, we will find the technology "in", "Virtual Server" (FCI) and "Windows server failover Cluster". We'll look at them in detail and summarize their location in the high availability stack. This will provide us with a good foundation, which is essential to lift the stairs. The high-level staircase will institute the required infrastructure and different storage requirements and options, using AlwaysOn availability groups and flood control information systems.

after each stair level you will get further understanding AlwaysOn builds. Although as a DBA, you may not have a direct role with core infrastructure projects in AlwaysOn and flood information systems, it helps to fully understand how all the technology is integrated. The last staircase will cause the feature's AlwaysOn configuration.

we will first look at the basics, including each of the 3 technologies already mentioned.

have for AlwaysOn describes abbreviations and abbreviations. We have included a list of common terms at the end of this article.

No more talking, let's delve into each of these technologies.

Windows server Failover cluster

Windows server failover cluster ( WSFC ha ) the products that sit under all of the high availability of Microsoft applications. By the world Sci-fi conference is windows sql Server alwayson High Availability group, even Microsoft exchange mail server cluster, you need to deploy and configure the WSFC

Windows Server failover clustering provides the ability to combine multiple computer nodes (physical and \ or virtual) into a set of applications for high availability services. Applications are server software, such as SQL Server or Exchange, and we want to be able to run on any node. A high-availability application can be obtained by providing a virtual access point to the client, including a unique IP address and a unique computer name or "virtual Network name". This address and virtual name become resources in the application group and are passed between participating nodes, such as tokens. A critical hardware failure of the active computer node will result in the loss of the group service running on that node. The Cluster service will automatically attempt to restart the group on the current node or on the partner node, depending on the type of failure (hardware or software).

At a higher level, the customer access point details are transferred along with any disk and service resources to the failover partner node. A failover of a clustered instance causes the client connection to be disconnected, and the client can reconnect when the service on the other node is available. Common failures are usually one of them, but any failure of the application can cause the service to migrate to another node:

Public NIC or network failure

Power failure

Motherboard failure

CPU Failure

with Wsfcs, a clustered application is installed into a different group or "app," which contains a set of resources, such as disks, services,IP addresses, etc. the group and its resources are resources that are owned by a node at any one time, cannot be from any other partner node unless a scheduled switch or failover occurs to that node.

A typical view of a Windows server failover cluster is as follows. Cluster nodes are connected over a network, and the domain controller and DNS service work with WSFC to allow clients to connect to virtual IP or virtual network names. No matter which node the service is running on.

for a fci deployment, the computer node must use shared storage, which is each node, Usually is from a three. For a typical alwayson Group of deployed nodes, leveraging their own local storage, rather than sharing with other cluster partners.

Although cluster nodes may have different hardware, it is often best to keep the hardware consistent across nodes to avoid situations where any weaker nodes must handle loads that exceed their capabilities. However, the nodes must use the same os patch level and network configuration; in Deployment windows windows Server version ( windows windows 2003, + node 8 nodes and windows 2012 The maximum cluster node count differs between the nodes.

Deploy a robust Windows Server failover clustering requires careful design, supported hardware, and An appropriate version of the Windows Server operating system. Geographically dispersed clusters (across multiple WAN clusters) Further increase the cost of design and planning requirements significantly increased as well.

It is to know that a WSFC is important to provide failover partner capabilities. These applications are not load-balanced and are not extended across nodes. Each service runs on only one node.

Typically, in a large multi-node cluster, you can Install the cluster application on a subset of Windows server failover cluster nodes. Making an installed application error on all nodes can cause some undesirable failovers, which we will see later, and also violate the AlwaysOn Group throttling policy, ensuring that all AlwaysOn instances reside on individual nodes in the cluster.

this by the world sci-fi Congress needs some form of mediation to control the ownership of cluster resources. This mediation is provided in the form of cluster quorum. Due to the Windows 2003 SP1, this quorum takes the form of a node voting system, with a majority of votes required to maintain a quorum. You can also share additional quorum resources by using a localized cluster of disks or a remote file for a multi-site cluster. From Windows Server ,quorums uses a dynamic node weight to configure the balanced cluster ticket to prevent unnecessary failovers during a dynamic scheduled outage. We will discuss more details on the future level of quorum.

Failover cluster instance

the failover cluster instance of SQL Server has been a popular high-availability technology in the case of the products in the system. A highly available SQL Server instance is clustered to mitigate any node hardware failures and any potential software failures. The only weak link here is storage, where the storage subsystem becomes the only point of failure.

of a failover cluster instance SQL Server instance, default or named, has been installed into a WSFC for the cluster application. Clustered applications typically have the following resources:

IP Address

Network Name

shared Disk (s)

SQL Server Service

SQL Server Agent Service

A separate instance shares the same basic requirements, except with a separate instance, The IP address and networkname are taken from the computer node and the disk that is stored on the computer is provided by local disk resources.

FCI 2 A typical view of a node cluster. sqlserver WSFC san LUN sql Server FCI is deployed in a 2 step process that will be at a later stair. Now, the following is the deployment of sql Server The failover cluster instance's 2

The first computer node will participate in the The FCI launches the new SQL Server Failover Cluster Installation wizard. Once completed and successfully completed, you are ready to proceed to phase 2 .

start The "Add node to SQL Server failover cluster Wizard for any computer node in WSFC, you want to participate in the new SQL Server FCI .

Note: Although the Standard Edition limits FCI 2 node, this does not indicate how many nodes have Windows Cluster Membership (you can have any number of the highest operating systems). This restriction is performed at the SQL Server setup level.

FCI is a bit like the runway relay switching process; The computer node has a clustered SQL Server application and resource, and provides access to the client's SQL Server Service (with batons). When the active computer node (Baton drop) fails, a partner node enters and takes over the cluster application and its resources (picking up the baton).

AlwaysOn Availability Groups

SQL server sqlserver service. alwayson integration Span style= "font-family: ' Times New Roman ';" >windows Server Failover clustering technology provides a more resilient, high-availability platform.

and clustering works at the instance level, AlwaysOn is configured at the database level. new technology for AlwaysOn availability groups, which describes the replication of a database of groups defined in SQL Server to a set of read-only partner instances, or replicas, because they are known in AlwaysOn . Multiple nodes each host has a synchronous copy of the AlwaysOn Database (S) and gets the best listener's configuration (more in this soon).

AlwaysOn availability groups require one or more secondary replica hosts to replicate the highly available database (S). These secondary databases may not be readable or readable. They can also be updated asynchronously or synchronously. Asynchronous replicas only support manual forced failover and synchronous replication supports automatic or manual failover.

Two read replicas may be configured to respond to read-only queries, and you can mitigate the stress on the primary database for minor backup/ maintenance operations. This primary and secondary relationship is also reversible to ensure true high availability. Any properly configured read-only partner can play a major role in the event of a failure within the system.

in Reliance on The WSFC core feature implements high availability,AO provides, but does not require any of the following resource shares to be associated with FCI .

Shared disk

shared IP Address

shared Network Name

shared SQL Servers and SQL Server proxy resources

there is one exception to this shared resource rule. When you create an audience in a group, this creates an IP address and the Network Name resource is shared by the AO Group copy.

as we have discovered, the weak links in the chain of failover cluster instances are shared storage. There are many ways to achieve redundancy, but it usually costs a lot and is often difficult to set up and maintain. Of course, as mentioned earlier, failover cluster instances only mitigate server hardware. It does not provide a single or even multiple secondary databases. prior to SQL Server , we had database mirroring in the server version, but these provided scopes only for a single, unreadable secondary database.

still use the familiar SQL Server AlwaysOn endpoint instance communication. Automatic configuration of endpoints when using the Availability Group Deployment Wizard. Wizard-driven deployment provides the simplest deployment path, while manual deployment requires a lot of human interaction. Nonetheless, a basic AlwaysOn group configuration is still very easy to deploy and configure and provide for HA, which is not previously available without resorting to feature integration complex levels.

You can also create a highly available listener service that you will use to receive incoming connections to the availability group. A listener consists of a unique IP address and a unique virtual network name. This is one of the most important changes that make a database highly available within a group.

a During the creation of an AlwaysOn availability Group, a clustered role is created within a Windows server failover cluster and contains a single resource. This resource is not a partner node during failover and the AlwaysOn Group is identified as an AlwaysOn primary replica group.

an AlwaysOn listener

listeners, when configured, will create resources and reside in the Failover Cluster application role AlwaysOn availability groups. Resources are

Virtual IP Address

Virtual Network Name

Listener uses The TCP port receives incoming connections and connects to the primary replica by default. When a read-only route is configured, the connection to the listener that specifies the read-only intent connection is routed to the secondary partner, not the primary replica. This is another way to mitigate the load on the primary replica.

of a failover cluster in an AlwaysOn group, both the application and the resource fail between the cluster nodes. The node location of the clustered application tracks the primary replica and its underlying nodes, and moves through the cluster as needed. The primary replica is a clustered SQL Server instance owned by the listener for the FCI \ Replica active node.

Conclusion

This sums up the stairs ' first1level, it provides a quick introduction3a core technology that allows us toSQLserver instances and their objects are highly available. In our high availability stack weWSFClevel for the base, which is aFCIorAlwaysOnBasic requirements for availability Group installation. Next We have the FCI, which sits atop the WSFC and relies on the cluster to serve and protect the SQL Server instance. Finally, ourAlwaysOnGroup, seated inSQL Serverand theSQL ServerA standalone instance of a failover cluster instance.

in Level 2 , we will look at the storage types available in SQL Server high availability and their typical usage. This will help you understand the horizontal series of future stairs.

Vocabulary List

AO	AlwaysOn Availability Groups
Fci	failover cluster instance for SQL Server
Tcp / ip	Transmission Control Protocol / Internet protocols. Network protocol used by Microsoft Client Network
Os/nos	Operating system /NOS
WSFC	World Sci-Fi Conference
LAN	Lan
WAN	Wan
Dns	Domain Name server
Dhcp	Dynamic Host Configuration protocol that automatically assigns IP addresses to network computers
IP Address	Ip Address
AD	Advertising
DR	Disaster recovery
Spf	Sun Protection factor
Scsi	Small computer System interface
ISCSI	Internet Small Computer System interface
Replica	Copies

Original Translation Link:

Http://www.sqlservercentral.com/articles/Failover+Clustered+Instance+ (FCI)/107536/

Translation (15)-----to Level 1 staircase: What is SQL Server AlwaysOn