Software-Defined Storage – The Devil is in the Details

The software-defined storage universe expanded today with the unveiling of VSAN by VMware and all of us at Maxta are excited by the news from our longstanding development partner, VMware. While it might seem a little strange to be excited for the arrival of a competitive product to Maxta’s MxSP, we have multiple reasons to be happy. The fact that VMware, a company highly regarded by everyone in the industry, has decided to dedicate the time, energy and resources to develop and bring to market a software-only product that helps enterprises reduce the cost and complexity of storage, underscores the challenges of traditional storage in virtualized environments and validates Maxta’s story.

That said, despite the VSAN announcement, MxSP is still the only VM-aware software-only solution that delivers convergence as well as end-to-end data integrity and data services that are essential for customers. Maxta pioneered this approach and has been shipping into production environments for well over a year, providing new levels of simplicity, agility, availability and cost. Essentially, MxSP is delivering today several critical capabilities that are fundamental for replacing storage arrays in all but a few cases while VSAN doesn’t provide these capabilities.

Maxta and VMware share a similar vision in many areas. We both believe that the separation of compute and storage, which made a lot of sense for legacy data centers, is not a good fit for modern data centers. Convergence of compute and storage on standard servers, leveraging server-side flash as well as magnetic storage, is the only way to meet the demands of modern data centers. However, in virtualized data centers, convergence alone is not enough. It is imperative to replace not only the storage array but also all legacy storage constructs such as volumes and LUNs by creating VM-aware storage and managing storage and data services at the VM level. Additionally, both Maxta and VMware believe in the software-only storage model, leveraging partners and the entire ecosystem to create multiple converged solutions to provide customers with multiple choices to best meet their individual needs.

There are two fundamental differences between MxSP and VSAN. First, MxSP is a fully integrated storage stack while VSAN provides only a piece of the storage stack, namely the aggregation of server-side storage to provide a highly available shared storage pool. VSAN doesn’t provide the data integrity and data services that customers expect. It relies on VMFS to provide the other piece of the storage stack. However, VMFS was originally designed to front-end highly reliable feature-rich storage arrays. Thus, the VSAN/VMFS combo approach is suboptimal. Second, VSAN is implemented in the kernel while MxSP leverages a VM form factor. So what do these differences mean to customers?

The MxSP integrated storage stack provides significant advantages over VSAN in the following areas:

Data resiliency:  MxSP supports end-to-end data integrity with strong checksums that protect each and every piece of data stored on flash or magnetic disk drives. This capability enables reactive on-the-fly as well as proactive determination of data corruption due to hardware or software issues. Once data corruption is detected, MxSP fixes it by leveraging another copy of the data. VSAN doesn’t provide a similar capability.

Enterprise-class data services: The MxSP novel data layout delivers an unlimited number of time, performance, and capacity-efficient VM level snapshots and clones. VSAN leverages VMFS for snapshots and clones. Due to VMFS design, it takes significantly longer to create or delete snapshots/clones. Additionally, each VMFS snapshot/clone imposes significant performance degradation. While some MxSP customers are utilizing hundreds best online casino or even thousands of snapshots concurrently, it is not practical to create more than a few VMFS snapshots concurrently.

Capacity Optimization: MxSP supports native capacity optimization capabilities such as compression and de-duplication. VSAN doesn’t provide a similar capability.

VSAN proponents point to the fact that VSAN has a performance advantage since it is implemented in the kernel. It is certainly true that the VSAN approach minimizes context switches and reduces the performance impact due to context switches. However, storage performance is impacted by multiple factors such as data layout, caching algorithms, and storage stack design, and not just by the number of context switches. Poor implementation of snapshots and clones cannot be masked by reduced context switches. To sum it up, MxSP customers who had the opportunity to participate in the VSAN beta told us that in most cases, MxSP performs better.

More importantly, time and again, it was proved that any approach that traded software development efficiency and portability to gain a performance advantage is not sustainable. A VM form factor provides a more efficient software development platform and a more portable architecture that supports a key customer requirement — Hypervisor Lock-in Avoidance.

MxSP architecture supports multiple hypervisors both for vSphere (5.0, 5.1, 5.5) as well as Hyper-V and KVM while VSAN supports only vSphere 5.5. We are working with our customers to refine support for Hyper V and KVM and you will hear from us soon. Being hypervisor agnostic provides investment protection, whether it is the ability to utilize another hypervisor from the get go or the desire to have multiple alternatives in the future.

VSAN is a great first step for VMware and serves notice to the marketplace that there is a better alternative to storage arrays. Maxta shares this view. However, MxSP is the only solution that fully delivers this vision today by providing all the capabilities that are required to truly replace storage arrays and thus streamline IT while delivering significant cost savings. We welcome VSAN to our universe!

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