VMware Virtual SAN vision to disrupt storage paradigm

virtualisation software

VMware Virtual SAN vision to disrupt storage paradigm

Antony Adshead

VMware has got eyes for storage. For a couple of years now the server virtualisation giant has incorporated useful features into its hypervisor to help manage shared storage.

But now VMware wants more, and it is setting out a vision to exert real control over storage, with plans that include storage virtualisation, replacing the logical unit number (LUN) with native VMware storage, pooling server flash, and the creation of a VMware Virtual SAN from direct-attached disk (DAS).

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In short, VMware has plans to virtualise storage just as it has done for servers. Suppliers of mid-range and enterprise arrays need to sit up and pay attention, because VMware could make them a thing of the past.

Since vSphere 4, the EMC-owned company has shipped tools in the hypervisor that have helped it work in tandem with storage arrays. These have included sets of application programming interfaces (APIs) and management functionality in, for example, the VMware APIs for Array Integration (VAAI) that offload storage tasks, including snapshots, mirroring and thin provisioning from VMware, and VMware APIs for Storage Awareness (VASA) that have allowed VMware administrators visibility into storage arrays.

There is also the Storage Distributed Resource Scheduler (DRS) functionality, which places, balances and moves virtual machines (VMs) to optimise their use of storage. And there is VMware’s Virtual Storage Appliance, which pools the disk resources of VM servers, but is limited to network attached storage (NAS) – NFS – functionality and scalability to no more than two or three physical servers.

Such functionality essentially augmented the storage array. While some storage actions can be carried out from the hypervisor, the job of the storage controller operating system – to virtualise and manage the physical media and to make it ready for the storage of data – was left pretty much intact.

Hypervisor muscles in on storage controller duties

But now VMware has set out a vision in which this work will be done in the hypervisor. At VMworld Europe 2012 in Barcelona, VMware set out these plans over a number of seminar sessions.

They comprise three main areas of product development, centred around storage virtualisation capability. VMware would not say when these will feature in shipping products, but said they would come “over the next few releases”.

Storage Policy-Based Management

The first is Storage Policy-Based Management (SPBM). This virtualises existing storage arrays and direct-attached storage to create pools of capacity based on performance characteristics. The storage administrator will carve out these pools and be able to assign storage to apps according to their need from the resources available. Wizards will facilitate the ability to specify the storage required according to capacity, input/output operations per second (IOPS) and availability in terms of recovery time objective (RTO).

“It’s policy-based automation; an orchestration engine for all apps across all storage that allows a storage profile ID card to be tied to a specific VM,” said VMware product manager Alberto Farronato.

SPBM does not step on the toes of storage product capability. It enhances it. But, the next two elements of the vision take a much bigger swipe at storage functionality.

Virtual Volume and Virtual Flash

The second set of features comprises Virtual Volume and Virtual Flash, both of which begin to appropriate functionality traditionally carried out by the storage controller.

Virtual Volume allows for VMDK files – complete virtual machines – to be stored natively on the storage area network (SAN) or NAS. This allows array-based features such as snapshots to be carried out per-VM.

Meanwhile, Virtual Flash targets caching and allows server-side flash to be managed in the same way as DRS currently manages CPU and memory in VM servers. In other words, it will allow server flash to be seen as a pool and for VMs to be moved around and matched to available resources with reservations and shares. Initially, it will be read-only, but it will be applied to writes subsequently.

VMware Virtual SAN

The final piece of the VMware storage vision is the VMware Virtual SAN. This takes existing virtual storage appliances to a whole new level and seriously treads on the toes of existing storage suppliers’ products.

VMware Virtual SAN will allow the creation of a virtualised pool of storage from distributed server direct-attached disk. It will have scale-out functionality and incorporate vSphere functionality, such as vSphere High Availability, DRS and vMotion.

According to VMware’s Farronato it will provide enterprise-level performance, with very high throughput and no bottlenecks due to its aggregation of many drives, and will suffer no single point of failure for the same reason. Likely use cases he cited were virtual desktop infrastructures (VDI), big data and disaster recovery. “It will likely run out of VM compute capacity before it runs out of storage,” he said.

The likely capacity of VMware Virtual SAN puts it firmly in the lower reaches of the enterprise array market. At present, design targets are that it can scale to a cluster of 32 server hosts with up to 36 (solid state and spinning) disk drives per host. That is 1,152 drives, which put it at the petabyte-plus level of capacity.

Storage suppliers beware of VMware

If VMware’s plans come to fruition, we could see it being able to manage a shared pool of petabyte-level capacity with native VMware storage. This could all prove severely disruptive to a number of storage suppliers.

The stated targets for scale and functionality of the VMware Virtual SAN potentially undermine the market for mid-range to lower-level enterprise SAN and NAS products.

Shared storage arose as a way of making storage easier to manage and to gain the most from its capacity. It was not an easy task to manage or share capacity across scattered DAS hardware. And with the rise of server and desktop virtualisation shared storage became a necessity, as it became far too difficult to match DAS resources to the I/O and capacity needs of a fluid server estate.

Shared storage used to mean a discrete SAN or NAS array. But that has begun to change over the past couple of years. Google famously uses its own home-grown storage based on clusters of scaleable server DAS, and products such as Nutanix’s storage server have arisen to provide that kind of configuration to the virtualisation market. Nutanix and products such as Tintri have gone for the VMware native market too, by allowing storage in VMDKs and the VMware Datastore format.

So, what we’re seeing in VMware’s storage vision is the inevitable conclusion of these developments. Storage arrays are essentially a bunch of disks with functions and intelligence provided by the controller. Meanwhile, VMware specialises in providing the intelligence to manage multiple instances of server hardware and software, and latterly some storage functions in the array too. It is, therefore, a logical next step for it to provide all the software intelligence of the storage array from the hypervisor.

Storage array suppliers that could suffer most are the ones with the most sophisticated functionality, said storage analyst and founder of StorageIO Greg Shulz.

“Those which have put a focus on extensive features, functionality and management tools to derive a premium fee will see the greatest pressure, as opposed to those which have basic storage systems. Lower-end basic iSCSI, SAS and Fibre Channel block storage solutions and suppliers were at a disadvantage against those with more feature/function-enabled solutions. But, by combining basic building block type products with virtual SAN type approaches, they can move up the stack,” he said.

Also likely to suffer are the storage products that have arisen to provide VMware-native storage such as Nutanix and Tintri. Those that sell virtual storage appliances may also see the rug pulled from under them. In this space are suppliers such as DataCore and HP’s Lefthand.

Of course, we have yet to see any of VMware’s visions for storage turned into an actual product, but there is no doubt it has the intention and capability to take the intelligence of the storage controller and place it in the hypervisor. VMware certainly has eyes for storage and looks set on bringing large chunks of it under its control.


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