Hyper-V Replication
Another new technology built-in to Windows Server 2012 is called Hyper-V Replication. Hyper-V Replication, shown in Figure 1,
allows a cluster node to replicate Hyper-V guest sessions from one
server to another server, typically across a WAN providing site
redundancy. If a server in one site fails, the guest sessions in a site
that has been replicated can be brought up in another site. This
concept has been realized over the past couple years through the use of
SAN snapshots, where data is replicated from one server to another
using expensive storage hardware. However, with Hyper-V Replication, no
SAN is required for data replication. In fact, all the technology
needed to initiate Hyper-V Replication is a source Hyper-V host server
and a destination Hyper-V host server. Just pointing the source to the
destination server can begin the replication of Hyper-V guest sessions
between hosts.
Figure 1. Hyper-V Replication between host systems.
Because Hyper-V Replication does not
require SAN snapshots or other fancy hardware, it makes the entry into
site replication a low-cost and simple task. With Windows Server 2012,
continuous availability now extends between sites; so, beyond local
clustering and high availability, organizations can now do disaster
recovery and business continuity with site-level guest session
replication.
Cluster-Aware Updating
With clustering as a major component of many
of the continuous availability technologies, the ability to patch and
update the cluster nodes without interruption to network services
becomes important for continuous availability. New in Windows Server
2012 is Cluster-Aware Updating (CAU), which enables, as part of the
patching and updating process, a method for cluster nodes to have
network services failed over, get patched and updated, and failed back
to an operational state. The CAU process simplifies updates and
minimizes system operations downtime during critical patches and update
cycles.
Improved Support for SANs
Windows Server 2008 and Windows Server 2012
support for storage-area networks (SANs) by providing enhanced
mechanisms for connecting to SANs and switching between SAN nodes. In
the past, a connection to a SAN was a static connection, meaning that a
server was connected to a SAN just as if the server were physically
connected to a direct-attached storage system. However, the concept of
a SAN is that if a SAN fails, the server should reconnect to a SAN
device that is now online. This could not be easily done with Windows
2003 or earlier. SCSI bus resets were required to disconnect a server
from one SAN device to another.
With Windows Server 2012, a server
can be associated with a SAN with a persistent reservation to access a
specific shared disk; however, if the SAN fails, the server session can
be logically connected to another SAN target
system without having to script device resets that have been
complicated and disruptive in disaster recovery scenarios.
