A data processing services firm said it boosted server performance significantly by replacing its servers' internal...
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disks with Intel X-25M solid-state drives (SSDs).
The company, which goes by the name richrelevance, serves personalized product recommendations for online retailers such as Sears, processing millions of requests each day over its five data centers. Each data center operates a farm of Dell and Hewlett-Packard servers with internal disks for parallel processing.
Each server continually receives new "models" of search patterns, which ideally can be held in DRAM cache. But Elya Kurktchi, senior director of IT and operations, said, "The challenge was that since we're sharing a great deal of data, we often had to travel to disk to fetch recommendations for customers." This process could take up to 100 milliseconds (msec), a bottleneck in richrelevance's business.
Last summer richrelevance considered adding RAM, but its existing servers didn't have room. That's when the company began eyeing the place occupied by spinning disk. "We were going to use an 'over the counter' SSD until we saw Intel's announcement [in August]."
The company had evaluated drives from Ridata and SanDisk, both of which used designs that were about a year old, Kurktchi said. "The performance of the new Intel drives blew the socks off the first-generation designs," he said.
The Ridata 32 GB drive showed 1,211 IOPS in mixed-read testing by richrelevance, while a 64 GB SanDisk drive yielded 2,163 IOPS. The 80 GB Intel X-25M produced 9,272 IOPS. Throughput tests measured 65 MBps, just under Intel's stated 70 MBps. In production, the drives have slashed latency from 100 msec down to 16 msec.
SLC vs. MLC: Longevity and cost
The M in X-25M stands for "Mainstream" and is a multilevel cell (MLC) version of Intel's new drives. Most enterprise SSD use cases have focused on single-level cell (SLC) drives thought to offer better endurance and data integrity. Kurktchi said richrelevance favored the MLC version because of its lower cost. "We got the X-25Ms for about $600 each for a total cost of $35,000. The X-25Es cost a lot more," he said.
The company's fast-changing environment and redundant parallel infrastructure also ease concerns about MLC drives, Kurktchi said. "The way we architect our infrastructure is highly redundant, and we don't expect data to be retained all that long because our model is updated frequently," he said.
Frequent writes to SSDs can shorten their life, but Intel claims two features will give all its X-25 SSDs better reliability than first-generation drives. The newer drives can reduce "write amplification," a phenomenon that speeds the wear of memory cells that must first be erased completely in 1 MB chunks before new bits of data can be written. Intel also said its SSDs have special algorithmic efficiencies for wear leveling among the individual NAND dies within the SSD.
"With first-generation drives, we would've used them up within about a year," Kurktchi estimated. "With these we're predicting five years."