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CHAPTER 1 What Kind of Protection do You need?
More and more, we see MSCS used for those applications that cannot provide availability
themselves, or as an internal component or plumbing for their own built-in availability solutions,
as opposed to an availability platform in its own right. Examples include Exchange cluster con-
tinuous replication (CCR) and database availability groups (DAGs), both of which we cover in
Chapter 7.
Application Built-in Availability
From 1997 to 2005, asynchronous replication was uniquely filling the void for both data protec-
tion and data availability within many Windows Server environments — and as we discussed,
Windows Server was not yet becoming commonplace except in larger enterprises with high IT
professional skill sets. But while the clustering was becoming easier for those applications that
could be clustered, another evolution was also taking place within the applications themselves.
Starting around 2005, Microsoft began filling those availability and protection holes by provid-
ing native replication and availability within the products themselves.
FI l e se r v I c e s ’ dI s t r I b u t e d FI l e se r v I c e s (dFs)
As the most common role that Windows Server is deployed into today, it should come as no sur-
prise that the simple file shares role that enables everything from user home directories to team
collaboration areas is a crucial role that demands high availability and data protection. To this
end, Windows Server 2003 R2 released a significantly improved Distributed File System (DFS).
DFS replication (DFS-R) provides partial-file synchronization up to every 15 minutes, while DFS
namespace (DFS-N) provides a logical and abstracted view of your servers. Used in parallel,
DFS-N transparently redirects users from one copy of their data to another, which has been pre-
viously synchronized by DFS-R. DFS is covered in Chapter 5.
sQl se r v e r MI r r o r I n g
SQL Server introduced database mirroring with SQL Server 2005 and enhanced it in SQL Server
2008. Prior to this, SQL Server offered log shipping as a way to replicate data from one SQL Server
to another. Database mirroring provides not only near-continuous replication but failover as well.
And unlike the third-party approaches, database mirroring is part of SQL Server, so there are no
supportability issues; in fact, database mirroring has a significantly higher performance than most
third-party replication technologies because of how it works directly with the SQL logs and data-
base mechanisms. By using a mirror-aware client, end users can be transparently and automati-
cally connected to the other mirrored data, often within only a few seconds. SQL Server database
protection will be covered in Chapter 8.
ex c h A n g e re p l IcA tI on
Exchange Server delivered several protection and availability solutions in Exchange Server 2007
and later in its first service pack. These capabilities essentially replicate data changes similarly to
how SQL performs database mirroring, but leverages MSCS to facilitate failover. Exchange 2010
changed the capabilities again. The versions of Exchange availability solutions are as follows:
SCC Single copy cluster, essentially MSCS of Exchange, sharing one disk
LCR Local continuous replication within one server, to protect against disk-level failure
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