When one talks about virtualization, the immediate thought that comes to mind is about server/ host virtualization otherwise understood from the virtualization offerings from the likes of VMware, Citrix, Microsoft, etc. However, there is a not-so-explored & not much known data center technology that can contribute significantly to a modern (future) data center. When we talk of real time cloud application deployment (access anywhere) with enterprise workloads, there should be something more that the Infrastructure should support, to enable effective consolidation and management of storage/ host infrastructure across a data center.
This article aims to introduce Storage Virtualization (SV) as a technology and the role this can play in enabling federated data services use cases.
The Need for Storage Virtualization
Traditional data centers are largely FC-SAN based, where monoliths of huge enterprise storage arrays are hosted, deployed, configured, and managed but with niche expertise. Most of mission critical applications of the world run on such data centers (DC). EMC (Dell EMC), NetApp, IBM, HP (HPE), etc. are a few major players in this arena. The appliances these companies have built are tested and proven on the field for the reliability, efficiency and availability across various workloads.
However, the major constraint of an IT investor of the modern times is related to the DC/ DR manageability and upgradability, more in the context of upcoming products with alternate technologies such as hyper converged storage; than defy the storage array based implementations. With vendor lock-in’s, rigid & propriety storage management API’s/ UI’s, it is a cumbersome process to think of an idea of having heterogeneous storage arrays with various vendors in a DC. Also, it poses the challenge of having skilled administrators who are well-versed on all different product implementations and management.
Before it was a hyper-converged storage, the storage majors ventured to innovate an idea that could possibly solve this problem. This is how Storage Virtualization was born – where a way was envisaged to have heterogeneous storage arrays in a DC but still could seamlessly migrate data/ applications between them through a unified management interface. Not just that, the thrust was to see a bigger picture of application continuity to data center business continuity scaling up the scope of the high availability picture.
What is Storage Virtualization?
Storage virtualization (SV) is the pooling of physical storage from multiple storage arrays or appliances into what appears to be a single storage appliance that can be managed from a central console/ unified storage management application. Storage Virtualization could be an appliance hosted between the host and the target storage or could be just a software VM.
Some popular SV SAN solutions available in the market are IBM SVC, EMC VPlex, NetApp V-series, etc.
Use case & Implementation - How does it work?
Let’s look at a practical data center use case of a heterogeneous data center, where there are 9 enterprise storage arrays, say 2 nos. of Dell EMC VMAX, 1 nos. of HPE 3PAR, 1 nos. of IBM V7000 & 5 nos. of EMC Clariion CX300. Consider that all legacy applications are currently hosted in EMC Clariion array and all the mission critical applications are hosted independently in EMC/ HPE/ IBM arrays. Let’s assume that the total data center storage requirements are already met and with the current infrastructure, it can easily support the requirement for the next 5 years. Consider, just between HPE, EMC and IBM arrays, we have sufficient storage space to accommodate the legacy applications as well. However, there isn’t a way yet to manage such a migration or a consolidated management of all different storage devices.
Now, let’s look at some of the use case requirements/ consolidation challenges that a storage consultant should solve:
- Fully phase out Legacy CX300 Arrays and migrate all the legacy applications to one of enterprise arrays say, IBM V7000, but with minimum down time.
- Setting up a new data center, DC2 about 15 miles away and moving 2 of the enterprise arrays, say 2* EMC VMAX arrays to the new site and host this as an active-active data center/ disaster recovery site for former DC (DC1).
- The current site, DC1 should become DR site for the new DC, DC2 however should actively engage I/O and business should continue. (Synchronous use case)
- Management overhead of using products from 3 different vendors should reduce and should be simplified.
- The entire cycle of change should happen with minimum downtime except for the case of physical movement/ configuration of VMAX arrays to the new site.
- The architecture should be scalable for data requirements of next 5 years in such a way that new storage arrays from existing or new vendors can be added with no downtime/ disruption.
- The DC & DR sites are mutually responsive to each other during an unforeseen disaster and are highly available.
This is a classic case for Storage Virtualization Solution. An SV solution is typically an appliance with software & intelligence that is sandwiched between the initiator (hosts) and the target (heterogeneous storage arrays). For the initiator, the SV is the target and for the target, the SV becomes the initiator. All the storage disks from the target (with/ without data) appear as a bunch of unclaimed volumes in the SV. As far as hosts are concerned, they appear to the SV as unmapped initiators unregistered. Storage- Initiator groups are created (registered) in the SV which can be modified/ changed on the fly giving flexible host migration at the time of server disaster.
There are different SV solutions available from vendors such as EMC VPlex that can help cases of local DC migration as well as migration between sites / DC’s. Let’s see how the solution unfolds to our use case requirements.
- Storage from both legacy array and the new array once configured to access the hosts through an SV solution, the storage disks/ LUNs appear as pool of storage at the DV interface. The SV solutions encapsulates the storage so that data migration between both the arrays can happen non-disruptively. Vendor1- Vendor2 replications are challenging and often disruptive.
- SV solutions are configured in a fully HA configuration providing fault tolerance at every level (device, storage, array, switch, etc.).
- Across site SV solution such as EMC VPlex Metro can perform a site-site data mirroring (synchronous) that too which both the sites are fully in active-active IO configuration.
- The entire configuration done through HA Switches provides option to scale to add existing/ new vendor storage arrays as well new Hosts/ Initiators with zero down time.
- The entire solution be it at local DC level or multi-site would be fully manageable through a common management UI/ Interface reducing the dependence on skilled storage administrators who are vendor specific.
- A SV solution consolidates the entire storage and host infrastructure to a common platform simplifying the deployment and management. Also, this sets a new dimension to hyper-converged storage infrastructure to be scaled across sites.
- A SV solution is agnostic, to the host and storage giving diversity of deployment options. For e.g. various host hardware, operating systems, etc.
- All the features of a storage array are complimented to its full potential along with superior consolidation across Storage/ sites with additional availability/ reliability features.
- Solutions like VMware vMotion does help in site- site migration, however, an SV solution provides the infrastructure support for that happen at the storage device level that too across sites.
It’s just a matter of time, when we will see more efficiently packaged & effectively deployed SV solutions. Perhaps, it could be called software defined SV solution that can be hosted on a VM instead of an appliance. Storage consolidation is a persistent problem, more so in the modern days, due to the diversity of Sever Virtualization/ SDS Solutions, varieties of Backup and recovery applications/ options available to an IT Administrator. There should be a point where DC should become truly converged where best of every vendor can co-exist in its own space complimenting each other. However, there is a business problem to that wish. For now, we can only explore more on what SV can offer us.