Dell tiering vs. a competing cache-centric hybrid: The power of “More”

Sometimes “less” is “more,” but other times not so much. It seems almost unfair to compare Dell Storage to cache-centric hybrids because, by using tiering instead of caching, Dell provides so much more raw flash and raw disk performance for the money. To check competitor claims of turning less into more, we engaged Evaluator Group to run tests modeled on real-world environments.

To cut to the chase, Evaluator Group summarized:

“Our testing found that for sustained workload performance, both Dell systems provided better performance as measured by higher I/O rates, lower latencies, and higher throughput than the competing system.”

We did some math to contrast the competitor claims to the test results.

While the competitor claims compression and no loss of flash capacity for hot sparing or parity overhead, the net results showed that the raw flash advantage for Dell translated directly into fitting larger data sets in flash. Evidently the competitor is subject to other forms of overhead that cancel the claimed benefits. Dell Storage SC4020 had 8x more raw flash for a similar price and held at least 8x larger data sets completely in flash compared to the competitor. Dell EqualLogic PS6210XS had 2.3x more flash and, net of compression and all forms of overhead, held 2.5x larger data sets in flash.

The competitor’s claimed benefit of not consuming any flash space to hold parity data did not result in better capacity efficiency than Dell; it did result in a 2.5x to 4x apparent performance drop for the competitor in the event of a flash drive failing.

While the competitor claims write optimization, the net results showed that for realistic workloads consisting of 40% writes, Read-Intensive (RI) SSD in SC4020 provided 2.6x more performance for a similar price than the competitor. Similarly, PS6210XS had an approximately 2.9x advantage in raw HDD IOPS and yet had an even larger 4x advantage for actual IOPS for data sets in HDD.

While the competitor claimed, in theory, faster reaction to changing workloads, the testing showed a large “Monday morning” risk and showed EqualLogic PS6210 to deliver better performance sooner in response to a cold area transitioning into a hot area.

The large Dell advantage in raw specs per dollar did translate into large customer advantages in usable flash capacity and over-all performance. In other words, “less” really is “less” and “much more” really is “much more.”

For more details, see our technical white paper: Dell tiering vs cache-based competitor.

About the Author: Rob Young