1.9 Storage Virtualization Overview

Similarly, just as we can virtualize the physical servers and applications we can also virtualize the storage systems to access the data. Storage Virtualization can be defined as the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console.

What is Storage Virtualization ?

Storage virtualization is the technique of abstracting physical storage resources like SSD's and HDD's to create virtual storage resources. Storage virtualization software has the ability to pool and abstract physical storage resources, and present them as a logical storage resources, such as virtual volumes, virtual disk files, and virtual storage systems. According to SNIA (Storage Networking Industry Association), There are 3 types of storage virtualization. 

Host-Based Storage Virtualization: 
Host-based virtualization is usually in the form of a logical volume manager on a host that aggregates and abstracts volumes into virtual volumes called logical volumes. Volume managers also provide advanced storage features such as snapshots and replication, but they are limited in scalability, as they are tied to a single host. Most companies don’t consider host-based storage virtualization as a true form of storage virtualization.

Also Read: Virtualizing Physical Servers and Applications

Network-Based (SAN-Based) Storage Virtualization: 
Network-Based storage virtualization is virtualizing storage at the SAN switch level which is a very complex type of storage virtualization and also rarely used by companies. At the network layer, it requires intelligent network switches, or SAN-based appliances, that perform functions aggregation and virtualization of storage arrays, combining LUNS from heterogeneous arrays into a single LUN and allowing heterogeneous replication at the fabric level which replicating between different array technologies. 

Controller-Based Storage Virtualization 
This is by far the most common form of storage virtualization and consists of an intelligent storage controllers that can virtualize the storage disks. The SNIA categorizes controller-based storage virtualization as either in-band or out-of-band. 

In In-band virtualization, the technology performing the virtualization sits directly in the data path. This means that all I/O of user data and control data passes through the technology performing the virtualization. Whereas Out-of-band virtualization which is also known as asymmetric has the meta data pass through a virtualization device or appliance and usually require special HBA drivers and agent software deployed on the host. It is less popular than In-band virtualization.

Advantages of Storage Virtualization

As with Server & Application virtualization, storage virtualization enhances your organization’s efficiency and agility and makes storage protection infinitely easier than with traditional physical storage architectures. These are the common benefits an oraganization can get by deploying storage virtualization.

Also Read: Understanding Traditional and Virtual Storage Provisioning
  • Agility: By breaking down the barriers between physical storage devices and creating a single storage pool and management interface, storage virtualization makes provisioning new storage for new company initiatives infinitely simpler. The management interface masks the underlying complexity of the physical storage devices, so you no longer have to deal with the individual quirks of each storage device. You don’t even have to know which devices you’re using. Instead, you can add or migrate storage simply by clicking on icons in a software application. Provisioning new storage is quick and painless, so you can respond to new business initiatives fast.
  • Efficiency: Intimately tied with agility is storage efficiency. Since provisioning and migration are so much easier, companies are no longer inclined to over provision storage in order to prevent time consuming upgrades.   
  • Thin Provisioning: Many storage virtualization solutions enable a feature called thin provisioning that makes provisioning even more painless and increases storage efficiency further. Thin provisioning allows file systems to pull new storage from a shared storage pool instantly at the moment they need to write to it, or based on thresholds you configure in advance. 
  • Performance: Some storage virtualization solutions let you stripe data across multiple drives, drive arrays, and network storage devices, regardless of different physical storage brands and products. This can enhance performance tremendously for high performance applications such as video manipulation.
  • Easy Management: Since storage virtualization pools storage from different devices and brands and presents it all under a single management interface, it makes managing storage much easier. You only have to master one interface instead of multiple. Troubleshooting storage issues is infinitely quicker and easier as well.  
  • Reduced Costs: Storage virtualization reduces both the capital and ongoing costs of storage. Since you’re no longer over provisioning storage, your initial storage capital costs are greatly reduced. And since provisioning and managing storage take less time and training your ongoing costs are reduced. Less physical storage also means lower power and cooling costs.
  • Automation: Data center automation is a new software category that is coming into its own with the advent of storage and server virtualization. With data center automation software, new resources can be provisioned to applications automatically when they are needed, say at peak use points of the day, then removed when they are not. Users can actually use some automation solutions to provision their own server and storage resources for new projects or test configurations without even having to call on IT.
Having discussed all the above points about the usage and benefits of Storage Virtualization, all these are leading the current storage administration to a next level called Software-defined storage administration which we will discuss in next posts.

Software-defined storage (SDS) is a storage infrastructure that is managed and automated by software. SDS abstracts heterogeneous storage systems and their underlying capabilities, and pools the storage resources. Storage capacity is dynamically and automatically allocated from the storage pools based on policies to match the needs of applications.

Previous: 1.8 Server and Storage Architectures Overview

                                                    Next: 1.10 Storage Connectivity and Network Virtualization
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