There is a lot of talk about virtualization these days. Server virtualization, hardware virtualization, application virtualization and also storage virtualization.

What is storage virtualization? Storage Virtualization involves the pooling of storage resources of similar or different capability to create and present logical subsets of that storage to devices such as servers.

There are several different types of storage virtualization including:

• Host/Server-based virtualization
• Network-based virtualization
• Storage device virtualization

Host/Server-based

This is how disk storage has been used for many years now. The physical device is handled through the use of device drivers and hardware intercepts. Physical devices are divided up into logical sections.

The downside of this type of virtualization is that once capacity is depleted new storage needs to be added. This is often limited by the servers storage bay capacity. Long term this is not a good solution.

Network-based

Has traditionally refered to fibre channel storage networks or Storage Area Networks(SANs). iSCSI storage can also be included in this type. OpenFiler is an OpenSource iSCSI platform that you can use to convert a server into a SAN.

The downside of fibre channel storage is the capital costs to purchase.

The benefit is you can add capacity and assign storage as required. It is also normally a redundant solition that can handle partial failing in the fabric.

Storage Device

Is often built into Storage Area fabric. The benefit of this type is that additional storage can be added downstream. These devices can usually handle migration and replication functions between controllers and disk sets.

This solution is normally the most expensive and complicated to establish.

All of these can work well by themselves, but the adoption of one method usually means you need to adopt a vendor specific solution. This might not be the best if you need vendor independence within your core systems.