The virtualised information store
The virtualised information store
Enterprise storage is not exactly known for inter-operability.
However, if storage virtualisation lives up to its promise, we ought to see
storage products from multiple vendors communicating seamlessly with each other.
by Anil Patrick R.
The strategy followed by most enterprises when it comes to
storage purchases is to stick to the one-vendor-offers-all approachespecially
when it comes to high-end SAN boxes. This has been mainly due to the incompatibility
of storage products from different vendors. In the past, such lack of inter-operability
rendered helpless many a brave soul who dared experiment with a mix-and-match
multi-vendor approach to storage. This scenario was endurable as long as enterprise
data grew at a relatively slow pace. But as mega data churners such as enterprise
wide applications began contributing to the information store, storage management
across varied storage devices became a nightmare. It therefore became imperative
that a single point of control to manage the entire organisations storage
infrastructure be put in place.
With enterprises focussing on cost, the need to derive optimum value and higher
application availability from storage has become top priority. It is difficult
to stick to one vendors products due to the functionality demanded by
ONE OF FIVE KEY ELEMENTS
The concept of storage virtualisation starts to assume greater importance at
this point of time. Virtualising storage is not a new concept. IBM has been
working on storage virtualisation since the 1970s. Even the traditional RAID
approaches used in DAS are a form of storage virtualisation.
Requirements like higher application availability, increased utilisation
and increased productivity with a single point of control have been the main
drivers for virtualisation, says Subram Natarajan, Senior Solutions Architect,
IBM South Asia.
As we shall see, the technology still has a long way to go. Storage virtualisation
technology is currently restricted to the SAN environment. However, if the technology
matures it has great potential. Theres still a little hype, but
virtualisation is one of the five key elements that will become a part of any
comprehensive enterprise storage network. The five elements are storage resource
management, storage network management, policy management, data management,
and virtualisation, says Sanjay Kharade, Principal Consultant, Cisco Systems,
India & SAARC.
BEHIND THE SCENES
The basic premise behind storage virtualisation is to have a consolidated storage
pool consisting of varied (heterogeneous) storage devices. The pool can be managed
from a central console. It can be accessed as a single logical volume or distinct
volumes as required. Storage virtualisation can be used where an organisation
has its data scattered over a number of devices. They can combine data and manage
it centrally, says Arindam Bose, GM, IT, LG Electronics India.
This is done by introducing a virtualisation layer that hides the complexity
of heterogeneous storage. Known as block-level virtualisation in SNIA (Storage
Networking Industry Association) parlance, this concept enables heterogeneous
storage to appear as a single logical volume to application(s). It is possible
to change volume or LUN (Logical Unit Number) size on the fly with storage virtualisation.
Storage virtualisation is needed if you have a complex heterogeneous environment.
It can be done at the server, switch and storage levels, says Rahul Singh,
Marketing Manager, StorageWorks Division, HP India.
|The virtualised info store
Inter-operability between heterogeneous storage may be a minor issue if
storage virtualisation delivers what it guarantees. However, it is yet to
gain mindshare in India due to problems like immature products and lack
of vendor participation in development of standards.
Storage virtualisation has the potential to solve today's storage
problems. That said, the technology needs to mature before it gains wider
This single logical volume approach helps write applications with fewer inter-operability
issues due to its device-independent nature. It helps reduce downtime since
the application isnt brought to its knees the minute a storage device
bites the dust.
Higher utilisation, compatibility with multiple operating systems, and the ability
to use storage from multiple vendors are all advantages conferred by adopting
this approach. Storage virtualisation helps storage administrators perform backup,
archiving and recovery easily, and in less time, by disguising the actual complexity
of the SAN. Some of the other advantages include easier data migration, automatic
capacity expansion, online disk-based recovery, and improved database performance.
This approach has several advantages on the operational side as well. For example,
consider an organisation which has dedicated servers for activities such as
reporting, accounting and Web services. These are attached to multiple storage
arrays among which many might have spare space while others may be highly utilised.
This creates a scenario where the total storage array capacity is utilised unevenly.
Combining these devices is intended to help organisations create higher amounts
of storage resources by optimally using existing resources. This also helps
servers running different operating systems to store information on the same
If implemented properly, storage virtualisation can result in cost savings and
higher availability. It can also help in mirroring requirements for DR purposes.
Pooling storage using storage virtualisation can help storage administrators
improve the abysmal 40 to 50 percent capacity utilisation rates that typify
most IT shops. Thats especially important for shops mirroring storage
to a secondary site, says Kharade.
THE FLAVOURS OF VIRTUALISATION
In a heterogeneous storage environment,
current storage complexities can be solved with the virtualisation approach
only with a thorough understanding of what it can do in a production environment
Virtualisation mechanisms available today use dedicated hardware
appliances or virtualisation software. The latter usually resides on fault-tolerant
Host-based storage virtualisation is waning in popularity
with virtualisation slowly moving into the fabric layer. Virtualising
the entire SAN is the latest storage virtualisation trend. SNIA refers to this
as block level virtualisation; it helps heterogeneous storage devices appear
as a single logical pool to applications, says Ajaz Munsiff, Director,
Virtualisation Products, EMC Asia Pacific.
In this context, the latest storage virtualisation buzzwords
on the fabric front are inband (symmetric) and out of band (asymmetric) virtualisation
approaches. Both use dedicated hardware to virtualise storage and have inherent
pros and cons.
The inband approach is the older of the two technologies,
and basically consists of a storage virtualisation device (appliance or controller)
situated between the SAN switch and the disk arrays. The SAN traffic is routed
through the device (usually a dedicated server) which provides the virtualisation
layer. This approach is followed by vendors like IBM and HDS.
By contrast, out of band-based storage virtualisation relies on the intelligent
features provided by layer 3 FC switches from Brocade, McData and Cisco. Virtualisation
is a by-product of the intelligence built into SAN switching devices. With SANs
moving towards intelligent networks, virtualisation comes by default, thereby
protecting the investment and reducing the cost of ownership of SANs. Intelligence
includes routing and software services support on each FC port, says Shuja
Mirza, Technical Consultant, India, Brocade Communications Systems.
One of the biggest problems cited against inband-based virtualisation by out
of band players is their potential for failure and slower I/O rates. Since the
SAN data traffic passes through the device, there is a probability of having
a single point of failure.
However, the fact remains that inband virtualisation is more widely accepted
now since the approach has been around longer than out of band. In addition,
virtualisation solutions for SMBs are provided only by inband players.
YET TO MATURE
As of now, storage virtualisation has yet to step outside the confines of a
SAN. The term storage virtualisation will become a reality only
when the concept manages to integrate all storage devices used in an enterprise.
According to Munish Mittal, VP, IT, HDFC Bank, there is scope for more agreement
among storage management vendors on the level at which virtualisation can be
implemented. It may probably work best when done at a level where data
really resides. The technology requires some amount of a common framework before
it becomes mature enough. This is why storage virtualisation is still at a nascent
stage from a practical point of view, opines Mittal.
|Time to consider storage virtualisation?
- Is it just for virtualising the SAN environment?
- Single point of control
- Sharing common storage pool between heterogeneous
- Increasing capacity utilisation
- Improving application performance
- Need for higher availability
- Disaster recovery capabilities (for example,
The lack of standards is the biggest setback plaguing storage virtualisation
today, although there is work going on for an SMI-S (Storage Management Initiative
Specification). Initiated by SNIA, the standard is not attracting sufficient
participation from storage vendors. Still in the process of evolution, the standard
is an attempt to dictate cross-platform inter-operability among storage products.
SMI-S has yet to be widely accepted. What is happening is that vendors
are choosing components rather than waiting for bodies to provide complete standards,
As of now, there are few takers for storage virtualisation in India. Indian
organisations are still wary and are waiting for the technology to mature. While
companies are interested, nobody has yet implemented a SAN virtualisation solution
as most vendors lack products and offer but a virtualisation roadmap,
Most Indian storage virtualisation projects are in pilot phase as of now. The
reason behind this is that storage virtualisation still has to prove itself
in production environments. In a heterogeneous storage environment involving
large amounts of data migration or data replication across storage sub-systems,
current storage complexities can be solved with the virtualisation approach
only with a thorough understanding of what it can do in a production environment,
Enterprises prefer to wait and watch for the technology to mature before they
take the plunge. We are still early even for large enterprise deployments
(in the range of 50 to 100 TB). We will see more deployments by next year and
by 2007 it will be mainstream. By 2008, storage virtualisation will be a done
thing, forecasts Munsiff.
As of now, vendors are suggesting the use of NAS headers to virtualise NAS devices.
Till the technology matures to the point where it becomes possible to virtualise
more storage devices than just the SAN, and standards are in place, the Indian
enterprise is likely to be fighting shy of storage virtualisation.
Even if complete inter-operability does not become possible, storage virtualisation
is maturing fast and for the betterin that direction. Let us give
it two years.