A FORSYTHE WHITEPAPER
Realizing the Promise of Storage Virtualization
Where Does Storage and Data Virtualization Live?
By Tony Johnson, Forsythe
S torage Virtualization holds great promise for many
IT organizations. This technology provides an
abstraction layer between traditional host and array
connectivity, without which, connected hosts on the
SAN are impacted by the storage environment. With
virtualization at the block level, each host no longer has
direct visibility to its back end storage array(s)—thereby
allowing daily operations, such as migrations, to occur in
a non-disruptive fashion. These types of activities are
normally disruptive to the stability of the storage
Two primary areas drive storage virtualization:
Data Mobility allows for data stored on logical units Storage and Data
(LUNs) within a storage array to be moved through a Virtualization Services
migration process. This migration process can be Before embarking on a storage virtualization endeavor,
movement within a storage array or to another location it is important to understand the purpose of the initiative.
outside the array. Movement within the array is often It is imperative that each customer keep three (3) clear
part of intra-array storage tiering that leverages a multi- goals in mind:
drive technology in one frame or footprint. Data mobility 1. Determine the key drivers for the solution or interest
is a large concern for a number of IT organizations: 2. Decide what is to be realized from virtualization
storage virtualization is an alternative to address the 3. Establish supporting ROI metrics to fund the
migration concerns by allowing the process to occur endeavor (if necessary)
without host downtime, relieving bandwidth capability
pressures on not just the storage team but also on all of
IT. With storage virtualization, metadata is used to Projects such as storage virtualization need to be
match virtual LUNs as seen by the host to physical planned and socialized to gain the appropriate budget
LUNs inside an array. The translation of virtual to for supporting the solution or direction. Storage
physical happens in the virtual layer thus allowing non- virtualization generally relies on hard and soft cost
disruptive movement of LUNs. savings around full-time equivalents (FTEs) and
application downtime. However, substantial cost
The promise of simplified management comes in savings may be found in tiering exercises such as re-
various forms. Virtualization allows a single raid, re-tier and the reclamation of storage made
management point for provisioning storage no matter available by the movement of storage data on LUNs
what back end arrays exist once the storage has been from more expensive storage tiers to lesser cost storage
provisioned to the virtualization layer using array-based non-disruptively, delaying the need to purchase more
tools. It also allows for more advanced functionality higher priced capacity.
such as replication, snapshots, clones and thin
provisioning, all managed from the same management In a recent industry study from the Gartner group, the
point. In fact, virtualization allows these functions determination of incorporating a services first approach
regardless of the capability of the back end prior to hardware procurement proved to be the most
prudent and profitable. Forsythe agrees with this
array(s). A case in point would be thin provisioning. An approach and affirmed that this strategy has helped
existing array may not be capable of thin provisioning; many enterprises achieve success.
however, with the addition of the virtualization layer, that
same array's LUNs can now be thin provisioned with
virtualization. Many professional services organizations support the
approach of Assessment & Design with "Best Fit"
vendor selection. Some of the mentioned organizations
in the Gartner study have vendor specific relationships
and some do not. The best return on the study would
be from an organization that has multi-vendor Furthermore, with server virtualization becoming
partnership so the customer can leverage the mainstream technology, associated storage
knowledge, familiarity and understanding in the areas virtualization becomes more compelling. The same
where they may not have a specific comfort level. efficiency and cost optimization drivers for servers apply
to storage. These drivers include:
The service offering should contain the following Data mobility across multiple heterogeneous
• Review and baseline current environment Automated and policy based management
• Determine conceptual technology solutions with ensuring that data is highly available and
financial impacts resides in the right place at the right time at the
• Determine vendor selection criteria with supporting right cost consistent with service level
scorecards agreements and objectives
• Provide final recommendations with clear prioritized Just as virtualization is changing the economics of
roadmap to success servers and applications, virtualization is also a logical
next step in the evolution of storage.
Concerns Tools to Support Storage Virtualization
Why Virtualize Storage? There are many tools available to companies when
When storage first evolved from direct attached to embarking on the storage virtualization endeavor. The
networked, the original challenges of inefficient organization must first understand the viability within
utilization were thought to be addressed. These areas their environment, the technical and economical
include: justification as well as potential pitfalls during integration
and operations. Enterprises have a choice to pursue
Storage island concerns with both internal FTE resources and outsourcing
Performance capabilities. Where there are clear upsides with an
Scalability external professional services organization regarding
time, tools and SME capability, the internal direction is
not without merit.
However, over time, networked storage and its
Many companies’ IT departments have the required
associated scale has produced its own set of
storage expertise and industry knowledge to support the
challenges. Instead of individual, direct attached storage
technical aspects. Many also have an internal project
islands, we now have SAN islands. In effect,
management organization (PMO) that keeps stated
heterogeneity has caused utilization and management
project initiatives on time and on task.
challenges. Even within one manufacturer’s product
line, different tiers of storage can have different
components, operating environments, and array-based Features and Functions
software and management tools. The key to storage virtualization is flexibility and
different approaches to "best fit" the pre-existing
environment. The endeavor must include FTE SME
Consequently, provisioning, expansions and upgrades, resources that understand the nuances between the
tuning and troubleshooting, recovery and lifecycle high-level direction as well as the technical depth and
management become complex, inflexible and labor detail at the physical solution base level.
intensive. This new set of pain points results in less
predictable performance, higher risk and increased cost HP Solution LeftHand SVSP
of ownership. Features Non-Disruptive Data Mobility
Performance Cost Effective
Popular belief seems to dictate that storage Scalability Disaster Recovery
virtualization adds unnecessary complexity and Availability Increased Uptime and
performance impact to a storage environment. Internal Simple Availability
array virtualization has been available for many management Easier server upgrade
generations of arrays, such as the HP LeftHand series, process
and has reduced the complexities of storage HA for multiple VM
management while increasing standard array image copies
performance. External virtualization solutions such as Functions Storage Clustering Heterogeneous
the HP SVSP may seem complex architecturally but Network RAID volume manager
lead to an overall simplification of the storage iSCSI Networking Business Copy
environment due to simplified management particularly Thin Provisioning Continuous Access
in a heterogeneous environment. With proper planning, Local & Remote Thin Provisioning
performance can be maintained and sometimes Copy Centralized, Role-
improved so that storage virtualization is a welcome based management
Understanding the required features and functions, with
a realization of business and economic focus to secure Storage Virtualization Industry Practices
the decision, is a pertinent piece to the readiness and Determining the business requirements and technology
procurement process. concern for a storage infrastructure is the initial step
when defining a storage direction that might include
The actual features and functions vary from solution to virtualization. Storage virtualization offerings have
solution. The HP solutions of LeftHand and SVSP vary matured the second half of this decade and are
as well. Here are a few key features and functions for continuing to capture interest. Storage administrators
each: are attracted to virtualization because the solution
unifies management, and managers like the technology
that will simplify data migrations and improve overall
operational efficiencies. Unification and simplification
In/Out of Band Management have been recognized as key contributors for driving
In-Band and Out-Of-Band management is in reference higher utilization rates. IT directors and CIOs are
to how storage virtualization has an impact on the actual pleased with the fact that virtualization can help further
input and output (I/O) traffic between a host server OS commoditize storage which provides additional leverage
and a source storage array. during negotiations driving lower costs.
An In-Band virtualization configuration is defined by Key Planning Questions
having the virtualization engine in the data path, which
receives the I/O requests from the host, and completes How are the business or application owners affected by
those requests to the array on behalf of the host. In application outages and what service levels are in place?
many cases, this could actually improve the response
Is there a storage services catalog that defines service
time from the host's perspective as the virtualization
levels back to the application?
engine will sometimes acknowledge I/O faster than
some aging or heavily utilized arrays. Once the requirements are determined, what will the
architecture and/or configuration look like?
Out-Of-Band virtualization is defined by having the What array or features are required?
virtualization layer not impact I/O traffic. The redirection
of I/O from host file system to physical storage happens Is storage allocation vs. utilization understood and is
at the hardware layer of the SAN switching architecture there an issue with over provisioning?
at wire speed with I/O acknowledgement coming from What is the storage chargeback model?
the array, not the virtualization layer. Control functions
of the virtualization engine and SCSI commands other What benefits will be gained by implementing a new
than reads and writes are carried out by an Out-Of-Band technology direction?
appliance that is not in the data path.
It is important to start educating internal customers on
how new technologies will directly affect them and how
Setting Polices processes could change. Storage centralization is a
Prior to setting the policy attributes within the fundamental part of any virtualization strategy and it is
virtualization solution, it is important to thoroughly important to start socializing this with the application
understand the policy requirements of the environment, owners encouraging them to move to a shared storage
applications, servers and lines of businesses the model if one is not already in place. Defining and
solution will be the central point of contact. Since standardizing a storage service catalog goes along with
storage virtualization allows a pass-through to storage centralization and moderation design
compatible legacy arrays, it is important to catalog, methodologies. By offering application owners storage
categorize and constantly inventory the support use of service levels, this provides a level of abstraction to the
the element behind the virtualization solution for business and will simplify the storage request process
appropriate alignment. thus adding flexibility to the way storage is managed
and provisioned to the customer. This helps remove the
speeds and feeds conversations that some application
As for setting policies, the management utility has many administrators can get hung up on, moving that
different configurations. It can be used out-of-the-box responsibility to the storage team.
and is highly configurable. Obviously, the out-of-the-box
policy definitions would be generic in nature and will
require administrative supervision for appropriately At a high level, storage virtualization can be placed into
assignments. It is highly recommended to complete the three categories or layers in the virtualization stack.
areas of catalog, categorization and inventory of current 1. Application or server operating system virtualization
usage and plot into a policy matrix for proper such as Symantec Foundation Suite is the first
configuration upon solution integration and category and the highest layer in the stack.
a. Basic virtualization functions such as RAID storage and lowering potential risk to the environment.
sets and volume mirroring The storage team will still require management tools
2. The second virtualization layer would be network or and optics that provide capacity reporting capabilities to
SAN fabric based services that include products help proactively plan storage upgrades and provide
like HP SVSP. sufficient lead times for the procurement cycle. It is
important to consider that adding virtualization to an
a. Advanced functionality like thin environment provides a new way of doing things and
provisioning, replication, data mobility thus required proper planning, testing and education.
across all virtualized storage
3. The lowest layer in the stack, and most widely used Automation and Operations
today, is array based virtualization
a. Advanced functionality like thin Automation
provisioning, replication, data mobility
inside the array Most storage virtualization products on the market today
contain some level of automation. Most of this
The higher up the stack storage is virtualized the more automation revolves around the ability to make PIT
storage becomes commodity and the less dependence (point-in-time) copies of data residing on a virtualized
there is on a particular array manufacturer and the array, or automated failover in the case of a disk array
software features that are in the array which help reduce or disk group failure.
The automation of PIT copy creation usually takes two
Three basic storage or data tiers would be part of a forms. First, the ability to schedule the creation of the
storage-virtualized infrastructure. copy through the management GUI, and that PIT copy
1. The first data tier relies on the most expensive software's ability to interface with a server or Virtual
fiber channel, feature rich high-end enterprise Machine and with a database on that machine to get a
class array. consistent
copy of the data at that point in time. Second, the ability
2. The second data tier is comprised of midrange to use CLI commands to create the PIT copy, for
low-end fiber channel or iSCSI enterprise class incorporation into user scripts. If an application is tied to
array. an array toolset (replication, cloning, etc.), it is important
to consider the impact of adding virtualization to these
3. The third data tier is a low-end fiber channel, applications and the scripting changes that may be
iSCSI, SAS (Serial Attached SCSI) array with required.
minimal feature set and functionality.
Both HP SVSP and HP LeftHand solutions offer
There are gaps between each tier and data movement automated creation of PIT copies of LUNs, both through
between tiers without virtualization is a labor intensive the management GUI and with CLI commands. Since
process that can induce unnecessary risk into the the destination storage pool can be selected ahead of
environment. Addressing the gaps between data tiers is time, the PIT copies could reside on lower tiers of
where storage virtualization, particularly at the storage within the same disk array, or in a different disk
application or SAN fabric services layers, can help close array. This allows the user the ability to enjoy the full
gaps within a storage infrastructure by providing unified useful life of a wide array of storage platforms for their
management, data mobility and higher storage storage tiers, and not be locked into each arrays
utilization rates. replication and management software tools.
When selecting a virtualization solution items to Both HP SVSP and HP LeftHand solutions offer
consider are product maturity, simplification, automated failover in the case of a disk array or disk
interoperability, and feature requirements. group failure, assuming the LUNs that are presented to
Interoperability is a critical item that can be overlooked servers have been correctly configured behind those
during the selection process. Checking qualification virtualization products to withstand a disk array or disk
matrices for server operating systems, HBAs, SAN group failure. This means using more than one disk
directors and switch, and array patch levels save array as a storage resource when creating LUNs for
considerable time during implementation or can presentation to servers.
potentially disqualify some solutions for an environment.
Product maturity is another important aspect and
customer references should be requested. Proper Operations
education is another requirement that should not be
One of the benefits of storage and data virtualization is
overlooked as storage virtualization is a net new
the ability to manage the day to day aspects of the
technology to the environment and should not be
storage environment such as provisioning through a
trivialized. This will help ensure a smooth
"single pane of glass". While being able to completely
implementation and transition to the new infrastructure
manage storage arrays from more than one vendor in
and help drive administration efficiencies by enabling a
one software tool is still some time away, for a variety of
storage administrator the ability to manage more
reasons, many of the common management tasks can
be performed with the incorporation of standards by storage arrays, or arrays from different vendors. The
storage service tier. ability to add software features to arrays that do not
have those features is a key benefit to SAN based
Once service level criteria are defined for each storage
tier, and arrays are chosen to support each storage tier,
those arrays can be completely configured in advance Both HP SVSP and HP LeftHand solutions offer a single
to meet those criteria. Storage virtualization platforms tool to manage storage assets, as well as to manage
can utilize LUNs once they are presented to it, so pre- replication for any storage that virtualized through them.
configuring the underlying storage arrays is a critical
step to enjoying management of the arrays from a single
Preparation Checklist for Storage Virtualization
Prior to deciding, procuring or sponsoring the installation
Here are examples of Tier 1 and Tier 3 service level of a storage virtualization solution, the customer should
criteria: have a keen understanding and awareness that any
storage virtualization solution is a technology enabler
Service Criteria / TIER 1 TIER 3
and is a part of the overall solution. Many customers
have operated under the misconception that the solution
is a utility that requires little pre-requisite planning or
LUN Sizes 50GB, 200GB 250GB, management after implementation. Complicating this
500GB fact is the thought that the solution will cure all issues
and concerns. Many items need to be evaluated both
RAID Level RAID 1 RAID 5
internally as well as during the solution selection
Drive Type Fibre Channel SATA, 7200 process.
(FC), 15K RPM RPM
Concerns Checklist of Preparation Questions
*The table above provides definition and detail around
Compatibility Are there challenges with
the terms expensive tier disk and lesser cost disk.
heterogeneous storage arrays?
With the service level criteria above, the disk arrays that Utilization What are the current utilization rates
have been selected to contribute to Tier 1 and Tier 3 within the storage environment?
storage would be pre-configured to those specifications, Reporting tools?
using the individual array's management software. All Protection Are there integrated software products
other functions would be handled by the virtualization for snapshot and/or remote replication
platform, such as LUN presentation and local/remote in use?
Solution What is the best course of action for
the current environment? (In-band or
Different standard LUN sizes were used above as a tool Out-of-band)
to help system administrators differentiate between
LUNs on separate tiers. Some virtualization solutions Performance What are the performance
allow pools of back end devices that can be used to requirements? (SLA, OLA, Storage
differentiate performance level LUNs from capacity level Catalog)
LUNs. Since the back end array characteristics can be
transparent, it is important to understand those back-
end characteristics to ensure application performance Simply stated, storage virtualization is a vehicle for the
and service levels with a virtualization solution. storage engineer, architect, manager and/or
administrator to simplify the provisioning of the storage
resources and reduce the heterogeneous complexity of
When using LUN sizes to differentiate between storage
storage infrastructure. The vehicle will require a
tiers, a base standard LUN size must be chosen, and all
thorough understanding as well as maintenance for a
LUNs created from that base should be a multiple of
smooth running machine.
that base. In the example above, a 25GB base LUN size
could be appropriate for all storage platforms in use.
Those base LUNs could then be combined to form a Many customers move into virtualization alongside
LUN of the desired size to be presented to a server. another event such as an array refresh. The majority of
virtualization solutions require a host outage as the
LUNs are moved from a standard array to host
Another benefit of storage and data virtualization is the
connection to a virtualized connection. Moving to
ability to enjoy the replication capabilities the
virtualized storage during a single outage that would be
virtualization platform offers regardless of the underlying
required anyway is a prime opportunity for most storage
storage array being virtualized. Those same replication
organizations. Other opportune times to move into
capabilities can also be enjoyed between dissimilar