microsoft sql server 2008r2 mirroring by: avinash kumar singh company: paxcel technologies pvt.ltd...

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Authored by: AVINASH KUMAR SINGH COMPANY: PAXCEL TECHNOLOGIES PVT.LTD Microsoft SQL Server 2008R2 Mirroring CONFIGURING SQL SERVER 2008 R2 MIRRORING

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Page 1: Microsoft SQL Server 2008R2 Mirroring by: AVINASH KUMAR SINGH COMPANY: PAXCEL TECHNOLOGIES PVT.LTD Microsoft SQL Server 2008R2 Mirroring CONFIGURING SQL SERVER 2008 R2 MIRRORING 1

Authored by: AVINASH KUMAR SINGH

COMPANY: PAXCEL TECHNOLOGIES PVT.LTD

Microsoft SQL Server 2008R2

Mirroring

CONFIGURING SQL SERVER 2008 R2 MIRRORING

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SQL SERVER HIGH AVAILABLITY SOLUTIONS

SQL SERVER DATABASE MIRRIORING

o Operates at the database scope. o Uses a single, duplicate copy of the database o Uses standard servers o Provides limited reporting on the mirror server by using database snapshots. o When it operates synchronously, provides for zero work loss through delayed

commit on the principal database.

Database mirroring offers a substantive increase in availability over the level previously possible with SQL Server and offer an easy-to-manage alternative to failover clustering.

Disk mirroring involves keeping two separate copies of a disk; while database mirroring lets solution providers create a single duplicate database copy.

Database mirroring has two advantages that failover clustering doesn't have. First, it operates at the database level instead of the server level, which means that database mirroring gives you much more flexibility than failover clustering.

The other advantage is that you can use standard servers for database mirroring. Microsoft recommends that customers purchase servers that are compatible with Windows Servers, but they don't have to buy hardware that is specifically certified for failover clustering. And, with database mirroring, you don't have to worry about the cost and complexity of using shared storage.

Proven SQL Server Architectures for High Availability and Disaster

Recovery SQL Server 2005 and SQL Server 2008 include many technologies that can be used to minimize

downtime and maximize data protection so that database administrators can ensure smooth

operation, continuous access to business critical data, and meet availability levels according to

various service level agreements.

Sometimes high-availability and disaster-recovery architectures are unfortunately designed

without considering the necessary business requirements—possibly there is already an

incumbent technology, or the designers are familiar with a certain technology and choose it as

the basis for a new architecture. This choice, when coupled with a lack of understanding of the

capabilities of the various high-availability and disaster-recovery technologies, can lead to an

architecture that fails to meet the business needs.

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It is imperative that the high-availability and disaster-recovery requirements of the business are

the drivers when evaluating which technologies are suitable as part of the architecture. The two

major business needs to consider are:

The duration of acceptable application downtime, whether from an unplanned outage

or from scheduled maintenance/upgrades (i.e. the defined Recovery Time Objective—

RTO).

The ability to accept potential data loss from an outage (i.e. the defined Recovery Point

Objective—RPO).

There is an existing whitepaper, “High-Availability with SQL Server 2008” (available at

http://msdn.microsoft.com/en-us/library/ee523927.aspx), that contains information about

each of the high-availability technologies in SQL Server 2008, as well as further links to other

whitepapers and technical resources. It also describes how to evaluate business requirements

and technical/non-technical limitations to help choose appropriate technologies.

However, there is a lack of information regarding proven architectures and real-life customer

deployments, where the high-availability and disaster-recovery architecture was chosen after

careful requirements analysis and technology evaluation.

This whitepaper provides a consolidated description of proven and commonly deployed high-

availability and disaster-recovery architectures, in terms of the technologies used and the

business requirements they are able to meet.

Furthermore, before committing to the implementation of any technology strategy, many

companies would like some level of reassurance that what they are attempting has been

successfully accomplished previously. To meet this need, Microsoft regularly publishes case

studies showing how their technologies have been used. This whitepaper also includes

references to relevant case studies of real-life customer deployments for each of the

architectures described.

Together these two whitepapers will provide the information necessary to allow the design of

an appropriate and successful high-availability and disaster-recovery architecture.

Failover Clustering for High Availability with Database Mirroring for

Disaster Recovery

In this architecture, failover clustering provides the local high availability and database

mirroring provides the disaster recovery capability. A failover cluster on its own protects against

physical server, Windows Server, and SQL Server failures but does not maintain a redundant

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copy of the data and so does not protect against a major outage like an I/O subsystem failure,

power failure, or failure of the network link to the primary data center.

Database mirroring is one way to provide a redundant copy of a single database on a separate

physical server, where the server can be in the same data center or geographically separated.

This architecture is widely adopted by customers who are familiar and comfortable with the

installation, configuration, and maintenance of failover clusters.

A typical implementation of this architecture involves a failover cluster in the primary data

center with database mirroring to a secondary data center or disaster-recovery site, as shown

in Figure 1 below.

Failover clustering combined with database mirroring

There are a number of variations and configuration options for this architecture depending on

the business requirements, including the following:

1. Each data center has a failover cluster with database mirroring between them. If the

business requirements state that the workload performance should not be impacted

after a failover to the secondary data center, the mirror server needs to have the same

hardware configuration (and hence workload servicing capability) as the failover cluster

in the primary data center. The alternative, of course, is to have a less capable stand-

alone server as the mirror server—however; this is not a recommend best practice.

2. Synchronous vs. asynchronous database mirroring. Synchronous database mirroring can

allow a zero data-loss requirement to be met, potentially with some workload

performance impact depending on the type of workload and the network bandwidth

between the two data centers. Asynchronous database mirroring does not guarantee

zero data loss in the case of a disaster, but has no impact on workload performance.

3. Automatic client connection to the secondary data center. If explicit client redirection is

used, the client specifies the FAILOVER_PARTNER in the connection string. After a

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database mirroring failover has occurred, the client simply has to reconnect and the

connection will automatically be made to the secondary data center. Alternatively,

some form of external routing can be used (some installations have used DNS routing,

for instance).

Configuring SQL SERVER 2008R2 Mirroring

Here we will show how SQL Server R2 clustering is configured .We have installed three

instance of SQL SEERVER on two nodes i.e. two servers .Following are the details of

server both the nodes are running under same DNS –Domain Name Service.

SERVERA -(PRINCIPAL SERVER)

SERVERB -(MIRRIOR SERVER)

SERVERB\WITNESS -(WITNESS SERVER)

1. Now configure the service accounts of SQL SERVER and SQL SERVER AGENT of the

entire instances under the same domain account as shown in the below screen

shot.Here we have configured them under pax\administrator.

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2. Now enable TCP/IP Services on all of the instances installed and restart the services

of SQL SERVER in order to bring changes to effect.

Note: By default TCP/IP is disabled

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3. Now at this point we have configured our instances now we need to configure our

database accordingly in order to achieve mirroring. First change the recovery

model at principal instance of SQL Server to full as shown.

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4. Now after changing the recovery model of database take the full backup of the

database as shown.

5. Copy that back file to the second node and then restore the database with NO

RECOVERY option as shown.

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6. Now at this point we have configured our database for mirroring .Now go to the

principal server i.e. SERVERA to configure mirroring services .Before that run the

following query on the on both principal and mirrored instance to give grant rights

to the login under which mirroring will be configured .

GRANT CONNECT ON ENDPOINT::Mirroring TO [PAX\Administrator]

Now launch mirroring on this database as shown

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7. After that on the pop-up window click on Configure-Security Button as shown.

8. After clicking on that button mirroring wizard will appear on the screen. Click Next

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9. After clicking next it will prompt including witness server as shown choose yes and

click next.

10. It will prompt to configure server instance just check the checkbox in front of witness server

and click next to proceed as shown.

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11. Now it will be by default connected to the principal server click next to proceed as

shown.

12. Now it will prompt to connect for mirrored instance just select the mirrored

instance i.e. SERVERB on which we have restored the backup as shown by giving the

required credentials and click next to proceed.

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13. Now it will prompt for the credentials for witness sever to connect, fill in the

required credential and click next to proceed as shown.

14. Now it will prompt for service accounts of SQL Server as shown we had configured

the entire instance on same domain account fill in the textboxes accordingly as

shown.

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15. After clicking next wizard will show the summary just review it and click finish as

shown it will configure endpoints for mirroring

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16. At this point we have configured mirroring now it will prompt for starting mirroring

services. Click on start button to start mirroring

17. Now at this point we have configured mirroring with high safety with automatic

failover (synchronous) -Requires a witness server instance. Commit changes at both

principal and mirror server if both are available. The witness server controls the

automatic failover to the mirror server if principal becomes unavailable as shown.

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18. Now a small change in the connection string of the .NET application will make it

accessible to the mirrored instance database as shown.

Data Source=myServerAddress;Failover Partner=myMirrorServerAddress;

Initial Catalog=myDataBase;Integrated Security=True;

19. We can even monitor database mirroring through Database mirroring Monitor as

shown.

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20. Register your database at the mirroring monitor

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21. Now you can monitor mirroring of your database from this console.

Why Mirroring, Why not clustering? We achieved this by zero downtime in the production environment and it is better

alternative to clustering because clustering requires much more downtime rather

than this one, more over Microsoft recommends that customers purchase servers

that are compatible with Windows Servers, but they don't have to buy hardware that

is specifically certified for failover clustering. And, with database mirroring, you don't

have to worry about the cost and complexity of using shared storage.

Also it operates at the database level instead of the server level, which means that database

mirroring gives you much more flexibility than failover clustering.

It also keeps the copy of database as in case of clustering there is only one making it

more venerable in case of disk failure