The New Storage Bottlenecks
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Tom Isakovich
Tom Isakovich,
User Rank: Apprentice
2/12/2012 | 8:09:25 PM
re: The New Storage Bottlenecks
Hi George,

Thank you for raising this critical topic. Most disk arrays are 6 to 1 "oversubscribed", relying on "expanders" to split a limited amount of bandwidth into 24 or more drive slots. This oversubscription is commonplace in the industry since even 15K rpm hard drives cannot push the IOps limit of this approach. But with flash memory, everything changes. In fact, just 2-3 flash drives or SSDs can overwhelm such expander-based approaches.

This is why a non-blocking architecture (one without oversubscription) is essential. Surprisingly, virtually all new "purpose-built SSD boxes" use the same old JBOD enclosures designed for disk arrays, just populated this time with SSDs. Such systems are no different and no better than just slotting SSDs into existing disk arrays.

In short, customers should ask their vendor to identify the data path in their systems end-to-end to make sure there in no oversubscription.

Tom Isakovich

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