Storage Virtualization

The storage industry has been constantly

evolving over the past so many years, and is expected to continue doing so in

the future as well. We saw storage technologies evolve from direct attached

storage to network attached storage and eventually into a storage area network.

All this has of course happened because of a heavy market demand for such

storage solutions. This has led to another challenge, that of managing such a

large and disparate storage infrastructure.

Storage virtualization aims to ease the administrative overhead and reduce the cost of managing

such a storage infrastructure. It also aims to reduce downtime and improve the

utilization of storage resources. Today, we're seeing various vendors coming

out with their own interpretations and implementations of storage

virtualization. This is a good sign, because it's an indicator that the

technology is being taken seriously. So now it's just a matter of time before

one standard emerges, and the technology becomes widely adopted.

The technology 



Storage virtualization presents a logical view of physical

storage by hiding the underlying complexity. It's like putting an abstraction

layer between the physical storage resources and the management interface. By

hiding all the physical storage complexity, the management of this entire pool

of storage resources is simplified. Moreover, all this has to happen without

sacrificing the performance and data integrity. Currently, all vendors have

their own implementations of storage virtualization, meaning you'll find

virtualization solutions for storage arrays, switching fabric, storage software,

and the like. 

Storage virtualization is not a completely new technology.

Take for instance, the age-old RAID or Redundant Array of Inexpensive Disks. The

technology combines storage capacity of multiple disks to make the storage more

fault tolerant and better performing. It's doing this by presenting one

logical view of multiple physical disks to the application. It's actually

storage virtualization in action. But life in the storage world has moved far

ahead, so this level of virtualization doesn't help. We're in the era of

high-speed networked storage, or SAN if you will, in which there are a disparate

number of storage resources, possibly all of them with RAID arrays, all

connected together and being accessed over a network. It's been a good move

from the older, dispersed direct attached storage resources in that

everything's centrally administered, but brings in its own administrative

headaches. You still have to manually create logical volumes out of the shared

storage pools for each server. You still have to manage all these volumes,

making it a fairly complex process, and requiring a high degree of knowledge in

storage management. Storage virtualization aims to automate many of these tasks

and yet provide the high performance and data availability needed. It aims to

simplify these challenges by helping automate various tasks, and bring

intelligence into the system such that it can monitor and manage all the storage

space allocated per server. 

Current implementations

 



Every storage vendor, be it for hardware, software, or
storage networking products have products based on their own definition of

storage virtualization. This leads to a lot of confusion in the customer's

mind. There's tremendous variation in the storage virtualization products

and likewise for the way they have to be implemented.

For example, storage array vendors host virtualization on

the storage controller; fabric switch vendors build it into their own products;

the storage software vendors have their own definitions and implementations and

so on and so forth. On top of that, each vendor claims that their implementation

is the best, which makes it difficult for the customer to really decide what to

choose. Add on top of that all the vendor hype that comes along with the

product.

Today, different vendors offer their own proprietary

solutions for storage virtualization, due to which interoperability still

remains a challenge. Another objective is to overcome interoperability issues

amongst different vendor products. 

The standards

 



Currently, SNIA or the Storage Networking Industry
Association has a definition for storage virtualization. It divides the

virtualization process into three parts-what's being virtualized, where's

it being virtualized, and how is it being implemented (see diagram). The first

part of what is being virtualized can include block-level, disk-level, tape,

file system, or file/record level virtualizations. The virtualization can be

done on a host or server, the storage network, or even a storage device such as

the switching fabric. Lastly, the virtualization could be in-band or

out-of-band.

Lastly, while there are various

implementations of storage virtualization, a lot still

needs to be done. Automation of various administrative tasks is one challenge

that needs to be addressed, such as creating volumes or adding a new storage

array. Using a policy-based framework for managing the storage infrastructure is

another challenge that needs to be addressed, such that the storage system can

automatically determine what type of storage is required for which type of host.

All this of course has to happen across a heterogeneous storage environment.

Currently, many of these features might be available, but wouldn't be

interoperable.