Flash-Memory Servers Make Bigger Splash
by Todd Spangler -- Multichannel News, 10/26/2008 8:00:00 PM
As cable operators continue to pack more onto their video-on-demand shelves — particularly HD programming — flash-memory-based VOD servers are gaining new fans.
Servers that use flash memory don't have any moving parts so they're more reliable than disk-based systems, which are susceptible to mechanical failure. And although solid-state storage is more expensive per byte than spinning disks, it also delivers higher performance.
Flash storage is three to 10 times more expensive than regular hard disks, depending on implementation, said Jim Brickmeier, Concurrent Computer's vice president of product line management. The key is to correctly size the flash-based servers based on usage patterns.
“You might have one piece of content that's 99% of the views, or you may have 20% of your content getting the majority of hits,” Brickmeier said.
Buckeye CableSystem, an operator in Toledo, Ohio, with 150,000 subscribers, this summer completed an upgrade to its VOD infrastructure from SeaChange International. The operator expanded from 2,500 hours of disk-based storage to 7,800 total, with about 1,000 hours on flash memory.
Jim Brown, Buckeye director of engineering, said flash VOD servers provide better performance and capacity for high-definition content and pave the way for time-shifted applications like Start Over, the service developed by Time Warner Cable to play back programs that have recently aired.
“We're really looking at it from a standpoint from some of the future services we're planning to offer,” he said.
Motorola is preparing to ship a flash memory option for its Broadbus VOD server line in the first quarter, to complement its original approach of using dynamic random access memory (DRAM).
Jim Owens, senior product marketing manager in Motorola's on-demand video group, said flash storage provides flexibility in designing VOD networks, but he maintained that DRAM is “the highest performance and has a much longer lifespan — that's still the gold standard.”
DRAM, however, is between 50% and 75% more expensive than flash, according to Edwin Ko, Harmonic's senior solutions manager for on-demand systems.
In addition, DRAM takes up far more space than flash media. Around 768 Gigabytes of flash memory fit into a two-rack-unit chassis, or 24 times the amount of DRAM storage that could fit into the same space, according to SeaChange vice president of product management Bang Chang.
“To do that you need to have a bigger [on-demand] cache, because once you go to HD you need four times as much storage,” he said.
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