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IBM and EMC represent two different approaches to enterprise-class flash-based storage.

The approach to utilizing flash for high-performance, enterprise use cases is evolving. Compute-intensive servers have already been enlisted to enable high-performance applications like enterprise resource planning (ERP), customer relationship management (CRM), online transaction processing (OLTP) databases, and more recently virtual desktop infrastructure (VDI). But a high-performance storage architecture to match the high performance compute has not yet been decided on. Flash seems to be the core of the solution, but where to put this flash for optimal enterprise performance? Announcements this week from EMC and IBM suggest two approaches: one server-based, one array-based.

One of the original strengths of SAN-based storage arrays was that they could support high-performance transactional databases at higher capacities. To improve performance, faster and faster hard-disk drives (HDDs) were employed in the array: 7,200 rpm, 10,000 rpm, 15,000 rpm. Eventually, flash-based solid-state drives (SSDs) were introduced with the ability to provide up to a 300X increase in IOPS over HDDs. Although more expensive, the performance benefits of flash SSDs have become too compelling not to support. This week, IBM announced SSD support for its XIV enterprise storage array, joining its own DS8000 series and every major storage vendor in offering flash SSD support for their enterprise class arrays.

But using flash as a storage tier in an array does not fully utilize its potential for performance. PCIe-based flash deployed in the server can offer up to a 20X increase in IOPS over array-based flash. Fusion-io has capitalized on this market with its ioMemory platform of flash-based PCIe cards aimed at accelerating high-performance applications, databases, and VDI, independent from the storage array. And just this past week, EMC’s announcement of VFCache, its own server-based flash product (previously code-named Lightning), shows that EMC is also embracing this approach and wants a piece of this growing market.

There are some drawbacks to current server-based flash solutions. Their capacities are smaller, they do not scale well in the server, they are not cache coherent between servers, and they cannot provide the enterprise data integrity and data management capabilities that flash in a storage array can. So while some of the highest-performance use cases may be moving to flash on a server, these issues will prevent primary storage from leaving the SAN any time soon.

There are also several flash-based solutions between the primary disk array and the server that offer different tradeoffs. “All flash” arrays like those from Violin Memory and Texas Memory Systems (TMS) can provide higher performance than typical tiered flash in an array, addressing the capacity and data integrity gaps of server-based flash, but at a higher cost. “SAN proxy appliances” like GridIron’s TurboCharger offer a less-pricey, high performance, flash-based caching solution for the SAN that can easily be dropped into an existing architecture. “Server network flash appliances,” such as EMC’s code-name Thunder, promise to address the limited scalability and shareability of server-based flash while retaining its higher performance.

As flash prices decrease, capacities increase, and as data integrity, cache coherency, and scalability are addressed, flash will continue its slow march towards the application. But it is clear today that flash in the server is an optimal solution for smaller data sets and highest performance, while flash in the array should be leveraged for larger or more mission-critical data sets, and a number of solutions in between can improve performance while balancing enterprise priorities with cost.