Chapter 10

Information Storage and
Management
Storing, Managing, and Protecting Digital Information
Ali Broumandnia, Broumandnia@gmail.com 1

Section II
Storage Networking Technologies
and Virtualization
In This Section:
• Chapter 5: Direct-Attached Storage and Introduction to SCSI
• Chapter 6: Storage Area Networks
• Chapter 7: Network-Attached Storage
• Chapter 8: IP SAN
• Chapter 9: Content-Addressed Storage
• Chapter 10: Storage VirtualizationAli Broumandnia, Broumandnia@gmail.com 2

Chapter 10
Storage Virtualization
• 10.1 Forms of Virtualization
• 10.2 SNIA Storage Virtualization Taxonomy
• 10.3 Storage Virtualization Configurations
• 10.4 Storage Virtualization Challenges
• 10.5 Types of Storage Virtualization
• 10.6 Concepts in Practice
• Summary

Key Concepts:
• Memory Virtualization
• Network Virtualization
• Server Virtualization
• Storage Virtualization
• In-Band and Out-of-Band Implementations
• Block-Level and File-Level Virtualization

Virtualization is the technique of masking or abstracting physical
resources, which simplifies the infrastructure and accommodates the
increasing pace of business and technological changes. It increases the
utilization and capability of IT resources, such as servers, networks, or
storage devices, beyond their physical limits. Virtualization simplifies
resource management by pooling and sharing resources for maximum
utilization and makes them appear as logical resources with enhanced
capabilities.

10.1 Forms of Virtualization
Virtualization has existed in the IT industry for several years and
in different forms, including memory virtualization, network
virtualization, server virtualization, and storage virtualization.
• Memory Virtualization
• Network Virtualization
• Server Virtualization
• Storage Virtualization

10.1.1 Memory Virtualization
Virtual memory makes an application appear as if it has its own
contiguous logical memory independent of the existing physical
memory resources. Since the beginning of the computer industry,
memory has been and continues to be an expensive component of a
host. It determines both the size and the number of applications that
can run on a host. With technological advancements, memory
technology has changed and the cost of memory has decreased. Virtual
memory managers (VMMs) have evolved, enabling multiple
applications to be hosted and processed simultaneously. In a virtual
memory implementation, a memory address space is divided into
contiguous blocks of fixed-size pages. A process known as paging
saves inactive memory pages onto the disk and brings them back to
physical memory when required.

10.1.2 Network Virtualization
Network virtualization creates virtual networks whereby each
application sees its own logical network independent of the physical
network. A virtual LAN (VLAN) is an example of network virtualization
that provides an easy, flexible, and less expensive way to manage
networks. VLANs make large networks more manageable by enabling a
centralized configuration of devices located in physically diverse
locations.

Virtual SAN (VSAN)
A virtual SAN/virtual fabric is a recent evolution of SAN and conceptually,
functions in the same way as a VLAN. In a VSAN, a group of hosts or
storage ports communicate with each other using a virtual topology defined
on the physical SAN. VSAN technology enables users to build one or more
Virtual SANs on a single physical topology containing switches and ISLs.
This technology improves storage area network (SAN) scalability,
availability, and security. These benefits are derived from the separation of
Fibre Channel services in each VSAN and isolation of traffic between
VSANs. Some of the features of VSAN are:

• Fibre Channel ID (FC ID) of a host in a VSAN can be assigned
to a host in another VSAN, thus improving scalability of SAN.
• Every instance of a VSAN runs all required protocols such as
FSPF, domain manager, and zoning.
• Fabric-related configurations in one VSAN do not affect the
traffic in another VSAN.
• Events causing traffic disruptions in one VSAN are contained
within that VSAN and are not propagated to other VSANs.

10.1.3 Server Virtualization
Server virtualization enables multiple operating systems and
applications to run simultaneously on different virtual machines
created on the same physical server (or group of servers). Virtual
machines provide a layer of abstraction between the operating
system and the underlying hardware. Within a physical server, any
number of virtual servers can be established; depending on
hardware capabilities (see Figure 10-1).

10.1.4 Storage Virtualization
Storage virtualization is the process of presenting a logical view of the
physical storage resources to a host. This logical storage appears and
behaves as physical storage directly connected to the host. Throughout the
evolution of storage technology, some form of storage virtualization has
been implemented. Some examples of storage virtualization are host-
based volume management, LUN creation, tape storage virtualization, and
disk addressing (CHS to LBA). The key benefits of storage virtualization
include increased storage utilization, adding or deleting storage without
affecting an application’s availability, and nondestructive data migration.
Figure 10-2 illustrates a virtualized storage environment. At the top are
four servers, each of which has one virtual volume assigned, which is
currently in use by an application.

10.2 SNIA Storage Virtualization Taxonomy
The SNIA (Storage Networking Industry Association) storage
virtualization taxonomy (see Figure 10-3) provides a systematic
classification of storage virtualization, with three levels defining
what, where, and how storage can be virtualized.

The first level of the storage virtualization taxonomy addresses “what” is
created. It specifies the types of virtualization: block virtualization, file
virtualization, disk virtualization, tape virtualization, or any other device
virtualization. Block-level and file-level virtualization are the core focus areas
covered later in this chapter.
The second level describes “where” the virtualization can take place. This
requires a multilevel approach that characterizes virtualization at all three levels
of the storage environment:
• Server
• storage network
• Storage
as shown in Figure 10-4.Ali Broumandnia, Broumandnia@gmail.com 17

10.3 Storage Virtualization
Configurations
Storage virtualization at the network is implemented using either the in-
band or the out-of-band methodology. In an out-of-band implementation,
the virtualized environment configuration is stored external to the data
path. As shown in Figure 10-5(a), the configuration is stored on the
virtualization appliance configured external to the storage network that
carries the data. This configuration is also called split-path because the
control and data paths are split (the control path runs through the
appliance, the data path does not). This configuration enables the
environment to process data at a network speed with only minimal
latency added for translation of the virtual configuration to the physical
storage.

10.4 Storage Virtualization Challenges
Storage networking and feature-rich intelligent storage arrays have
addressed and provided specific solutions to business problems. As an
enabler, virtualization should add value to the existing solution, but
introducing virtualization into an environment adds new challenges. The
storage virtualization solution must be capable of addressing issues such
as scalability, functionality, manageability, and support.
• Scalability
• Functionality
• Manageability
• SupportAli Broumandnia, Broumandnia@gmail.com 21

10.5 Types of Storage Virtualization
Virtual storage is about providing logical storage to hosts and
applications independent of physical resources. Virtualization can be
implemented in both SAN and NAS storage environments. In a SAN,
virtualization is applied at the block level, whereas in NAS, it is applied
at the file level.
• Block-Level Storage Virtualization
• File-Level Virtualization

10.5.1 Block-Level Storage Virtualization
Block-level storage virtualization provides a translation layer in the SAN,
between the hosts and the storage arrays, as shown in Figure 10-6.
Instead of being directed to the LUNs on the individual storage arrays,
the hosts are directed to the virtualized LUNs on the virtualization device.
The virtualization device translates between the virtual LUNs and the
physical LUNs on the individual arrays. This facilitates the use of arrays
from different vendors simultaneously, without any interoperability
issues. For a host, all the arrays appear like a single target device and
LUNs can be distributed or even split across multiple arrays.

10.5.2 File-Level Virtualization
File-level virtualization addresses the NAS challenges by eliminating the
dependencies between the data accessed at the file level and the location
where the files are physically stored. This provides opportunities to
optimize storage utilization and server consolidation and to perform
nondestructive file migrations. Figure 10-7 illustrates a NAS environment
before and after the implementation of file-level virtualization.

10.6 Concepts in Practice
EMC Invista and Rainfinity are EMC product implementations of
block-level and file-level virtualization, respectively. These
virtualization solutions offer improvements over traditional
device-level controls in the area of capacity utilization, storage tier
management, performance optimization, and data protection.

10.6.1 EMC Invista
EMC Invista is an out of band SAN-based block-level storage
virtualization solution. It uses intelligent SAN switches with
customized hardware to virtualize physical storage in a logical
presentation. These switches are capable of handling data
operations at network speed. These switches are capable of
handling data operations at network speed. They use specialized
software to examine the port, logical volume, and offset to which
the I/O is sent and can control the target path of I/O s to the
storage devices. Invista is physically located between the
production hosts and the storage arrays, as shown in Figure 10-8.Ali Broumandnia, Broumandnia@gmail.com 28

Invista Components
Figure 10-9 shows the hardware components of an Invista instance.

Invista Operation
When an I/O request from a host arrives at the DPC, it handles the
I/O and maps it to the appropriate virtual target (or initiator), as
shown in Figure 10-10.

Invista Advantages
EMC Invista provides block-level storage virtualization in
heterogeneous storage environments. It also supports dynamic
volume mobility for volume extension and data migration between
different storage tiers without any downtime. Invista supports local
and remote replication functionality; and it integrates with the
existing SAN infrastructure and uses the full fabric bandwidth for
high-speed I/O processing. Invista provides separate data and
control paths for easy management and faster I/O processing.

10.6.2 Rainfinity
Rainfinity is a dedicated hardware/software solution for file-level
virtualization. The Rainfinity Global File Virtualization (GFV)
appliance (see Figure 10-11) provides an abstraction of file-based
storage transparently to users. Files can be moved from one file
server to another even when clients are reading and writing their
data.
• Rainfinity Components
• Rainfinity Operations
• Global Namespace Management
• Rainfinity AdvantagesAli Broumandnia, Broumandnia@gmail.com 33

Summary
Virtualization provides flexibility while easing management of the
existing infrastructure. Virtualization enables users to optimally
utilize current processes, technologies, and systems. It allows for the
addition, modification, or replacement of physical resources without
affecting application availability. Virtualization technology offers
high security and data integrity, which are mandatory for centralized
computing environments. It also reduces performance degradation
issues and unplanned downtime due to faults, and ensures increased
availability of hardware resources. This chapter detailed the different
forms of virtualization and their benefits.

It also covered block-level and file-level storage virtualization and
provided associated product examples, explaining their processes. The
data mobility features in virtualization ensure uninterrupted storage
operation and prevent application outages due to any resource conflict or
unavailability. Resources and data are still vulnerable to natural disasters
and other planned and unplanned outages, which can affect data
availability. The next chapter covers business continuity and describes
disaster recovery solutions that ensure high availability and uninterrupted
business operations.

Chapter 10

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Chapter 10