The Semantics of Storage Virtualization
Have you embraced and deployed storage virtualization in your environment yet? When I ask this question to IT professionals, usually very few answer yes.Storage virtualization is more common than many, even company's that have deployed it, believe. Virtual tape, volume managers, and in some cases the systems themselves, are places organizations often go virtual.
However, when I rephrase the question and ask who is using virtual tape, volume managers, certain vendors' storage systems, including network attached storage (NAS), along with other technologies not commonly thought of as virtualization, the number of hands in the air increases significantly.
The fundamental idea behind virtualization is to abstract, emulate and facilitate aggregation among different capabilities. Figure 1 below shows how storage-related virtualization techniques and technologies can be deployed to address more than storage pooling and volume management in an IT environment.
|Figure 1: The many faces and locations for storage and I/O virtualization|
NAS systems are not often thought of as an example of storage virtualization, particularly if your definition of storage virtualization is focused on volume management and LUN pooling by an appliance or intelligent switch. But the reality is that many NAS solutions on the market embrace and leverage virtualization techniques in the form of abstraction and aggregation in many ways.
NAS systems that support virtual servers can move workloads across physical servers much in the same way applications and virtual machines enable server consolidation and flexibility of management. Another example of how some NAS systems are leveraging virtualization is the use of virtual storage pools and transparent data migration across different tiers of storage, along with integration into enterprise (ENS), global, (GNS) and clustered name spaces (CNS).
Storage Virtualization Myths and Realities
Some of the more common myths and misconception's involving storage virtualization include:
Myth: Virtualization can only be done in an appliance or on a network switch.
Reality: Virtualization can be done at many different locations in many different forms, including on a server using software, on an appliance using software, in a storage system or on a switch using software and hardware. Where to put and deploy the technology depends on your needs and preferences.
Myth: Virtualization is only for LUN and volume pooling management.
Reality: That has been the rallying cry for many years to get you to look at cost savings and shift to a different model for managing your storage. Ask yourself if volume pooling is a need-to-have capability that you can build a business case around, or if it is a nice-to-have technology for your specific needs.
Myth: Virtualization eliminates vendor lock-in.
Reality: Virtualization technology moves the point of vendor lock-in elsewhere, such as from a storage system to software running on a switch or appliance or host server. For example, there is a view that if you go with a Cisco, Brocade or QLogic switch with storage virtualization services enabled, you are locked into one of those vendors. However the reality is that you are locked in to specific software being used on those switches or appliances. While the potential exists with any hardware platform, lock-in or vendor "stickiness" occurs with virtualization software and features on which you become dependent. The golden rule with storage virtualization is that whoever controls the metadata or virtualization functionality controls the vendor lock-in.
Myth: There is no software available for storage virtualization appliances or switches.
Reality: Software exists from vendors such as EMC/Invista, IBM SVC, Fujitsu (Brocade), StoreAge (acquired by LSI yesterday), Neopath, Attune, Incipient, FalconStor, Diligent, Sepaton and others. However, not all software can run on a switch or appliance or host server, and feature functionally will vary with each vendor and implementation.
Myth: Virtualization reduces the cost of managing storage.
Reality: The potential for real and virtual cost savings exists but is not guaranteed. For example, if your focus is to save costs on storage hardware, take a look at the larger picture of additional platform and storage management software tools, recurring maintenance and software fees. You may be more effective looking at different storage options, particularly those that included embedded storage virtualization capabilities from block and NAS-based storage vendors.
Myth: Virtualization is half-baked and not ready for prime time.
Reality: This very much depends on how you are using and applying the generic term storage virtualization. Whether you're talking about an appliance-based solution, virtual tape, switch-based virtualization or other technology will dictate the maturity and availability of solutions. The reality is that some technology is more mature and robust than others, and in other cases it's a combination of both the hardware and software needing more time to evolve. A common problem I come across and hear about from IT customers is where technology is being pushed to do more than it was intended to do, combined with high expectation levels, particularly when it comes to performance-scaling capabilities.
Storage Virtualization Considerations
If you are not already leveraging or planning on deploying some form of virtualization technology to address your data and storage management challenges, the following questions will help you plan and be better equipped to sort out the various options.
- Keep in mind the issues or challenges you are looking to address with virtualization technology. For example, are you looking at volume, LUN or file system pooling and aggregation to improve capacity utilization, enhance interoperability, reduce management complexity, reduce costs or eliminate real or perceived vendor lock-in?
- Ask yourself if you need or simply want virtualization technology. For example, you may want to have virtualization to create a seamless transparent pool of unified storage to reduce costs and eliminate vendor lock-in. Or you may need virtualization to enable transparent data migration and movement for tiered storage or to eliminate downtime caused by technology upgrades or disruptions from capacity movement and allocation.
- How will virtualization technology fit into your existing environment? Look at what procedural and configuration changes will be needed, along with training and education requirements. What other technologies will be required on host servers, including applications, agents, managers, drivers, shims or other forms of software?
- Understand how a candidate virtualization solution or technology will scale in terms of number of storage devices and servers attached, overall capacity, performance (IOPS, bandwidth, latency) capabilities, ease of use and availability.
Greg Schulz is founder and senior analyst of the StorageIO group and author of "Resilient Storage Networks" (Elsevier).
This article was originally published on Enterprise Storage Forum.