Saving Money with Solid State Drives - EnterpriseStorageForum.com

Saving Money with Solid State Drives

Solid state (SSD) and flash drives are everywhere, thanks to high performance and falling prices.

SSD prices are still an order of magnitude or two above that of hard disk drives, but data storage vendors nonetheless seem to have grasped how to present the concept so it sells. Still, recent news of order delays at EMC (NYSE: EMC) — the largest customer of enterprise SSD maker STEC (NASDAQ: STEC) — suggest that SSD adoption might not be quite as rapid as its biggest proponents had hoped.

But the sales growth has still been impressive, even more so considering that it's occurred in the worst recession since the 1930s.

Lou Przystas, a senior advisory consultant at the corporate executive briefing center of EMC, served up a good example of how vendors expect to entice everyone to jump aboard the SSD bandwagon.

He laid out an example within an array to highlight how SSD will initially replace Fibre Channel (FC) disks — at least to some degree. And helped somewhat by SATA too.

The original 55TB configuration of the array consisted of 244 FC disks, each with 300GB and running at 15k rpm. By reducing the number of FC disks to 136, adding 32 1TB SATA disks along with eight 73GB SSDs, you arrive at the same 55TB capacity. On top of that, however, you get a whole lot more lot more performance, lower power consumption and reduced cost.

This is accomplished by implementing tiers of storage. SSD isn't cost effective enough or big enough in terms of capacity to dump everything on it. And it's unlikely that this will happen, at least in the near term. What should be done, then, is to put performance-critical data on flash, as well as key applications. Przystas even suggests loading key parts of a large application on flash and having the rest of the application run on lower storage tiers.

EMC will soon add automated tiering to make the most of flash drives, technology that's also offered or planned by other vendors.

With smart use of SSD and SATA in the above scenario, the end result is 28 percent fewer drives, 60 percent more drive IOPS, 21 percent savings in power and cooling, and 17 percent lower drive costs. The numbers in terms of IOPS are roughly 80 IOPS for SATA, 160/200 IOPS for FC and 5,000 IOPS for flash.

A big reason for these gains is the parallel read capability of flash that delivers an access time of 1 ms or less. The fastest FC disks, on the other hand, have response rates anywhere from 10 to 60 ms. Further, if done right, there is little performance deterioration on flash during heavy usage — unlike FC, which chokes off badly above a particular point. The worst flash is likely to get under the heaviest loads is an access rate falling to about 3 ms, which explains flash's appeal for top-tier storage and applications.

As for fears that flash isn't as durable as disk, Przystas pointed out that EMC offers the same five to seven year warranty for flash as it does for SATA drives. And he expects that to go up over time.

Although SSD costs are high, they have come down a lot during the last year. One SSD equals the IOPS of 30 15k FC disks. By setting up SSD for the fastest applications and the most heavily used data, FC for the second tier, and SATA for volume storage of less frequently accessed data, big gains can be realized.

A real world example concerns an Oracle-based transaction telecom billing system. By swapping 4 percent of the FC drives to SSD, the response time was lowered by 60 percent. In this case, swapping 16 out of 384 FC drives to flash resulted in big gains. The original FC disks with striping for performance could manage 12 ms at best. Flash brought that down to 1 ms or less.

"Transaction-intensive applications with heavy IOPS on reads are great for flash," said Przystas.

How about price? While most try to compare flash with hard drives, that is missing the point. The real comparison for now concerns flash with RAM, with the former being about 50 times less expensive. The latest SSDs even harness RAM to speed up writes, which was an early criticism of the technology. EMC predicts that flash will be priced very close to the cost of FC in about three years. When that happens, disk sales could be in trouble.

"Flash is revolutionizing the industry," said Przystas. "There will come a time when we are saying, 'Remember when we had spinning disks?'"

Article courtesy of Enterprise IT Planet

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