Marvell to release DRAM, SSD-based accelerator card

Accelerator card to address storage network saturation from server virtualization

SANTA CLARA, Calif. -- Solid-state drive chip maker Marvell Technology today announced that later this year it will release an accelerator card designed to deliver a tenfold increase in storage network throughput by caching and sorting data at the server before sending it to back-end arrays.

The new product, the DragonFly Virtual Storage Accelerator (VSA), was designed for the virtualized server environments that have been saturating storage networks in recent years, Marvell said in an announcement at the Storage Networking World conference here.

"Virtualization solved a big problem in past: It addressed low server utilization rates. But it also created a new problem: When you have many virtual machines in a server, it can bottleneck performance on one of three things -- the CPU, the network bandwidth or storage I/O," said Shawn Kung, Marvell's director of product marketing.

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The DragonFly Virtual Storage Accelerator

The number of chip sockets is increasing, clock speeds are improving and Gigabit Ethernet LANs are growing more common -- therefore the biggest performance problem typically lies with storage I/O, Kung explained.

"Even if each individual [virtual machine] has a workload profile that's sequential, the combination of so many VMs all trying to write I/O to the back end results in the arrays seeing a very highly randomized write pattern," Kung said.

The DragonFly VSA card comes in a PCI Express (PCIe) form factor, allowing it to be used in servers regardless of the protocol used to attach to back-end storage, Kung said.

The DragonFly is powered by what Marvell calls its "HyperScale" embedded processor technology, an ASIC (application-specific integrated circuit) that controls nonvolatile RAM as L1 cache and SSD chips as L2 cache to maintain highly consistent writes by placing them in sequential order, according to Kung.

"What's happening is we gather writes in cache and reorder them before staging them to a SAN or NAS array. The way it works is it coalesces the writes and then prunes the overwrites, the multiple updates and edits, so that the effective number of write [I/O per second] drops by 10 times," Kung said. "We've proven this in real-world benchmarks."

Marvell claims that no changes to applications are required for the accelerator card to perform and that it is storage agnostic, meaning it can work with NAS, SAN or DAS.

Arun Taneja, founder and lead analyst with market research firm Taneja Group, said the DragonFly VSA represents a "paradigm shifting product," because it will make a huge difference in enhancing the speed with which VMware and other hypervisors will bring mission critical applications under the purview of server virtualization.

"The biggest issue holding back IT from running mission critical applications as virtual machines is the lack of I/O. Putting one of these cards in the server will suddenly add tons of I/O. That would, in turn, make the applications run faster," Taneja said. "Many mission critical applications are latency sensitive. They will gain the most from this card. Bringing mission critical apps under VMware is one of VMware's top objectives for 2011. This will help big time."

Taneja said the new accelerator card will also be attractive for use in private and public cloud infrastructures, which are built on virtualized environments, but he pointed out that because the card resides in a server, it won't help with the I/O performance of other servers in a data center that don't have a DragonFly, where adding SSDs to a storage array can help the performance of all application servers connected to that box.

"Many vendors are trying to solve the I/O problem but in different ways. Examples are Avere, Pliant, Fusion IO, Violin, and so on. But those are all at the storage level. Marvell is doing it at the server level and that separates them from the crowd," he said. "I like what I see."

More and more often, user companies are adding SSDs to SAN and NAS arrays as a Tier Zero layer of storage, or a layer above high-performance hard drives, that offers vastly better I/O than standard hard drives. Abhijeet Gole, Marvell's senior director of engineering, pointed out that adding SSDs to a storage array helps improve read performance, but it typically causes write performance to deteriorate quickly to the point where it's no better than that of a hard drive.

Gole was referring to the fact that NAND flash memory in SSDs requires that every time a new data write comes in from a host system, an old block of data on the memory must be marked for deletion -- a process known as the erase-write cycle. When all blocks have been written to, firmware in the controller then sets about deleting data in stale blocks -- a process known as garbage collection. Garbage collection can severely hamper the performance of SSDs over time, and flash drives can only sustain so many erase-write cycles -- typically 10,000 for consumer-class drives and 100,000 for enterprise-class drives.

Gole also pointed out that, unlike storage acceleration appliances that use SSDs and in some cases DRAM as a cache in front of storage arrays, the DragonFly VSA scales linearly because as more cards are added to servers, the processing and storage capacity increases.

"That's a key difference in the way the DragonFly operates. It has L1 DRAM cache that buffers the SSD so you don't hit that random-write cliff," Gole said. "You can still have SSDs in your SAN or NAS array, but you're not going to get as high I/OPS as you will with a host cache."

The DragonFly VSA is undergoing initial tests with select Marvell customers. It's expected to go into beta testing this summer and will be available about three months after that, Kung said. Pricing has yet to be set, he said, but added that the cards will sell for under $2,000.

Lucas Mearian covers storage, disaster recovery and business continuity, financial services infrastructure and health care IT for Computerworld. Follow Lucas on Twitter at @lucasmearian or subscribe to Lucas's RSS feed . His e-mail address is lmearian@computerworld.com.

Copyright © 2011 IDG Communications, Inc.

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