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Symmetrix DMX: Is it Hot or Not?

The year is still young, but EMC's Symmetrix DMX announcement is arguably 2003's biggest storage story.

The year is still young, but EMC's Symmetrix DMX announcement is arguably 2003's biggest storage story. The question is: Does it deserve the hype? End users seem to think so. "I like the matrix idea over the switch-based concept, and more of everything will always make a techie drool," said one anonymous user, a storage manager at a Canadian bank that two years ago defected to HDS Lightning 9900 arrays. But based on the strength of the new Symm, he says he's "looking forward to dealing with the new EMC."

In terms of speeds and feeds, Symmetrix DMX is clearly an improvement over its predecessor. By moving from mirroring (RAID 0) to parity RAID, DMX has slightly more usable capacity than a Symm 8000 (37TB vs. 34TB), but uses fewer disk drives (288 vs. 384). Connectivity is up from 32 ports on the 8830 to 96 front-end ports on the DMX 2000. Last but not least, cache bandwidth improved dramatically. By switching from a bus to so-called matrix architecture, Symmetrix DMX got a 40X boost in aggregate cache bandwidth, up from 1.6GB/s to 64GB/s --compared to 15.9GB/s on Hitachi's 9980V array.

Or did it? EMC's claims to 64GB/s aggregate cache bandwidth (128 direct connections through cache at 500MB/s) is what Arun Taneja, an independent analyst in Hopkinton, MA, calls "a marketing spec number." "The more important number is 16GB/s"--the performance that a fully loaded DMX 2000, with its eight caches, can actually sustain (each with four regions, accessed simultaneously at 500MB/s), Taneja says. By way of comparison, HDS's 9980V has an effective internal cache bandwidth of 6.4GB/s.

On other fronts, DMX remains vulnerable to the HDS 9900 in terms of capacity, with only 37TBs, compared to the 9980V's 128TB. DMX is also missing a mirrored cache, although it does support a new error mitigation algorithm called Triple Modular Redundancy with Majority Voting. Only time will tell if this will satisfy users. "I'd hate to have a Florida situation," says Phil Townsend, HDS senior director of product marketing. "What happens then? A recount?"

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