Designing a Microsoft SharePoint 2010 Infrastructure Vol 2 part 27 docx

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Planning Business Continuity 14-15
Lesson 2
Developing a Business Continuity Plan for
SharePoint Server 2010

There are several strategies, technologies, and aspects to consider when you
develop a plan for business continuity in SharePoint Server 2010.
This lesson describes the key processes and strategies that are available to provide
high availability and disaster recovery for your SharePoint Server 2010
environment.
Objectives
After completing this lesson, you will be able to:
• Plan for availability in SharePoint Server 2010.
• Describe the strategies for database availability in SharePoint Server 2010.
• Describe the difference between failover clustering and high-availability
mirroring.
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14-16 Designing a Microsoft® SharePoint® 2010 Infrastructure
• Plan user-controlled business continuity features.
• Plan for disaster recovery in SharePoint Server 2010.
• Use log shipping for disaster recovery in SharePoint Server 2010.
• Identify considerations for high-level business continuity planning.


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Planning Business Continuity 14-17
Planning for Availability in SharePoint Server 2010

Key Points
You must make several key decisions when you plan your availability strategy for

an implementation of SharePoint Server 2010.
Evaluating Costs
As you plan your availability requirements, you must be aware that the greater the
degree of availability and the more systems that you decide to protect, the more
complex and expensive your availability solution is liable to be.
Be mindful also that not all of the scenarios in your organization are necessarily
going to require equal levels of availability. You might decide to provide different
degrees of availability for different sites, different application services, or different
farms.
When you plan your investment in an availability solution, you must consider the
following costs:
• Additional hardware and software, which can increase the complexity of
interactions among software applications and settings.
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14-18 Designing a Microsoft® SharePoint® 2010 Infrastructure
• Additional operational complexity.

You should evaluate the costs of improving availability in conjunction with your
business needs. Do all of your services require the same level of availability?
To gauge your organization's tolerance for downtime for a site, service, or farm,
you must ask yourself the following questions:
• If the site, service, or farm becomes unavailable, will employees be unable to
perform their expected job responsibilities?
• If the site, service, or farm becomes unavailable, will business and customer
transactions stop, leading to a loss of business and customers?

If you answer yes to either of these questions, you should invest in an availability
solution.
Choosing an Availability Strategy and Level
There are several approaches to increase the availability of your SharePoint Server

2010 environment, but the most typical approaches are to:
• Improve the fault tolerance of your server hardware components. Fault tolerance of
hardware components is the redundancy of hardware components and
infrastructure systems such as power supplies at the server level. When you
are planning for fault tolerance of hardware components, you must:
• Be aware that complete redundancy of every component in a server may
be impossible or impractical. Use additional servers for additional
redundancy.
• Ensure that servers have multiple power supplies connected to different
power sources for maximum redundancy.
• Obtain fault-tolerant hardware from your hardware vendors that is
appropriate for the system, including redundant array of independent
disks (RAID) arrays.
• Increase the redundancy of server roles within your farm. SharePoint Server 2010
supports running server roles on redundant computers within a farm to
increase capacity and provide basic availability. The capacity that you require
determines both the number of servers and the size of the servers in a farm.
After you have met your base capacity requirements, you may decide to add
more servers to increase overall availability.
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Planning Business Continuity 14-19
Choosing Database Availability Strategies
To support the availability of databases in your SharePoint Server 2010
environment, you can use Microsoft SQL Server® failover clustering or SQL Server
high-availability database mirroring.

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14-20 Designing a Microsoft® SharePoint® 2010 Infrastructure
Introducing Strategies for Database Availability in
SharePoint Server 2010

Key Points
To support the availability of databases in your SharePoint Server 2010
environment, you can use SQL Server failover clustering or SQL Server high-
availability database mirroring.
SQL Server Failover Clustering
You can use SQL Server 2008 with Service Pack 1 (SP1) and Cumulative Update 2
failover clustering to provide availability in a SharePoint Server 2010 farm. A
failover cluster is a combination of one or more nodes or servers, and two or more
shared disks. A failover cluster instance appears as a single computer, but has
functionality that provides automatic failover from one node to another if the
current node becomes unavailable for any reason. SharePoint Server 2010 can run
on any combination of active and passive nodes in a cluster that SQL Server
supports and that interprets the failover cluster as a whole entity. Therefore,
failover is automatic and seamless from the perspective of SharePoint Server 2010.
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Planning Business Continuity 14-21
SQL Server High-Availability Mirroring
Database mirroring is a capability in SQL Server that you can use to gain database
redundancy for your SharePoint Server 2010 databases. You implement mirroring
on a per-database basis and it works only with databases that use the full recovery
model. Database mirroring provides significant availability and presents an
alternative or addition to failover clustering or log shipping that is far easier to
manage.
If you want to use database mirroring to gain high availability for your SharePoint
Server 2010 farm, you need to use high-availability database mirroring. This is also
sometimes referred to as high-safety mode with automatic failover. High-availability
database mirroring differs from standard database mirroring in that it uses the
following three server instances:
• A principal server. This server instance serves the database to clients, and its

copy of the database is the current principal database. This role is the same for
standard database mirroring and high-availability mirroring.
• A mirror server. This server instance acts as a hot standby or warm standby
server, depending on the configuration and state of the mirroring session. Its
copy of the database is the current mirror database.
In standard database mirroring, the principal and mirror servers communicate
and cooperate as partners in a database mirroring session. The two partners
perform complementary roles in the session: the principal role and the mirror
role.
• A witness server. Unlike the principal server and the mirror server, the witness
server does not serve the database. The witness server enables SQL Server to
automatically fail over from the principal server to the mirror server by
regularly verifying whether the principal server is running correctly. The
mirror server instigates automatic failover only if the mirror server and the
witness server remain connected to each other after both have been
disconnected from the principal server.

There are two operating modes for configuring database mirroring:
• Asynchronous. This does not require a witness server instance, which means
that there is no automatic failover. When the database server is not available,
an administrator must stop the database mirroring session manually.
• Synchronous. You can optionally configure this by using a witness server. If you
do so, you get the benefit of the automatic failover feature. Synchronous mode
with a witness server is recommended for high availability.
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14-22 Designing a Microsoft® SharePoint® 2010 Infrastructure
You can use SharePoint Central Administration or Windows PowerShell cmdlets to
identify the failover, or mirror, database server location for your database after you
have configured a database mirror instance of SQL Server. By setting a failover
database location, you add a parameter to the connection string that SharePoint

Server 2010 uses to connect to the server running SQL Server.
In the event of a time-out event on the server running SQL Server, the following
occurs:
1. The witness server that is configured for SQL Server mirroring automatically
swaps the roles of the primary and mirror databases.
2. SharePoint Server automatically attempts to contact the server that is specified
as the failover database.

Additional Reading
For more information about SQL Server failover clustering, see

For more information about how to configure SQL Server database mirroring, see



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Planning Business Continuity 14-23
Comparing Failover Clustering and High-Availability
Mirroring

Key Points
There are several differences between the database availability strategies that the
previous topic introduced. The following table compares those strategies by using
several key considerations and factors.

Factor SQL Server failover clustering SQL Server high-availability
mirroring
Time to fail over Cluster member takes over
immediately upon failure.
Mirror takes over immediately

upon failure.
Transactional
consistency?
Yes. Yes.
Transactional
concurrency?
Yes. Yes.
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14-24 Designing a Microsoft® SharePoint® 2010 Infrastructure
Factor SQL Server failover clustering SQL Server high-availability
mirroring
Time to
recovery
Shorter time to recovery
(milliseconds).
Slightly longer time to recovery
(milliseconds).
Steps required
for failover?
The database nodes
automatically detect failure;
failover is seamless and
automatic.
The database automatically
detects failure; SharePoint Server
2010 is aware of the mirror
location, so failover is automatic.
Protection
against failed
storage?

Does not protect against failed
storage; storage is shared
between cluster nodes.
Protects against failed storage
because both the principal and
mirror database servers write to
local disks.
Storage types
supported
Shared storage (more expensive). Can use less expensive direct
attached storage.
Location
requirements
Cluster members must be on the
same subnet.
Principal, mirror, and witness
servers must be on the same
local area network (LAN) (up to 1
millisecond latency roundtrip).
Recovery model SQL Server full recovery model
recommended. You can use the
SQL Server simple recovery
model, but the only available
recovery point if the cluster is lost
will be the last full backup.
Requires SQL Server full recovery
model.
Performance
overhead
Some decrease in performance

may occur while a failover is
occurring.
High-availability mirroring
introduces transactional latency
because it is synchronous. It also
requires additional memory and
processor overhead.
Operational
burden
Set up and maintained at the
server level.
The operational burden is larger
than for clustering. Must be set
up and maintained for all
databases. Reconfiguring after
failover is manual.