Enhancements to High Availability with Windows Server 2008 R2

■ Hot add CPU and memory When using SQL Server 2008 R2 in conjunction
with Windows Server 2008 R2, database administrators can upgrade hardware
online by dynamically adding processors and memory to a system that supports
dynamic hardware partitioning. This is a very convenient feature for organizations
that cannot endure downtime for SQL Server systems running in mission-critical
environments.

■ Failover clustering Greater high availability is achievable for SQL Server R2 with
failover clustering on Windows Server 2008 R2. Windows Server 2008 R2 enhances
the failover cluster installation experience by increasing the number of validation
tests within the Cluster Validation Wizard. Moreover, Windows Server 2008 R2
introduces a Best Practices Analyzer tool to help database administrators reduce best
practice violations. Similar to its predecessor, Windows Server 2008 R2 continues to
supports up to 16 nodes within a failover cluster and organizations can also protect
their applications from site failures with SQL Server multi-site failover cluster support
by using stretched VLANs built on Windows Server support for multi-site clusters.
64 CHAPTER 4 High Availability and Virtualization Enhancements

■ Windows Server 2008 R2 Hyper-V The Hyper-V virtualization technology improvements
in Windows Server 2008 R2 were the most sought-after and anticipated
enhancements for Windows Server 2008 R2. It is now possible to virtualize heavy SQL
Server workloads because Windows Server 2008 R2 scales far beyond its predecessors.
In addition, database administrators can achieve increased virtualization availability by
leveraging new technologies, such as Clustered Shared Volumes (CSV) and Live Migration,
both of which are included in Windows Server 2008 R2. Guest clustering with SQL
Server 2008 R2 in Windows Server 2008 R2 Hyper-V is also supported.

■ Live Migration and Hyper-V By leveraging Live Migration and CSV—two new
technologies included with Hyper-V and failover clustering on Windows Server 2008
R2—it is possible to move virtual machines between Hyper-V hosts within a failover
cluster without downtime. It is worth noting that CSV and Live Migration are independent
technologies; CSV is not required for Live Migration.

■ Cluster Shared Volumes (CSV) CSV enables multiple Windows servers running
Hyper-V to access Storage Area Network (SAN) storage using a single consistent
namespace for all volumes on all hosts. This provides the foundation for Live Migration
and allows for the movement of virtual machines between Hyper-V hosts.

■ Dynamic virtual machine (VM) storage It is possible to add or remove virtual
hard disk (VHD) files and pass-through disks while a VM is running. Support for hot
plugging and hot removal of storage is based on Hyper-V. This is very handy when you
are working with dynamic SQL Server 2008 R2 storage workloads, which are continuously
evolving.

■ Second Level Address Translation (SLAT) Enhanced processor support and
memory management can be achieved with SLAT, which is a new feature supported
with Hyper-V in Windows Server 2008 R2. SLAT leverages Intel Virtualization Technology
(VT) Extended Page Tables (EPT) and AMD-V Rapid Virtualization Indexing (RVI)
technology in an effort to reduce the overhead incurred during mapping of a guest
virtual address to a physical address for virtual machines. This significantly reduces
hypervisor CPU time and saves memory for each VM, allowing the physical computer
to do more work while utilizing fewer system resources.