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Many of you may have heard of a poem written by Robert Fulgham 25 years ago called “All I Really Need to Know I Learned in Kindergarten.” In it he provides such pearls of wisdom like “Play fair,” “Clean up your own mess,” “Don’t take things that aren’t yours” and “Flush.” By now you’re wondering what any of this has to do with storage technology. Well the #1 item on the kindergarten knowledge list is “Share Everything.” And from my perspective that includes DAS (direct-attached storage).

Sharable DAS has been a primary topic of discussion at this year’s annual LSI Accelerating Innovation Summit (AIS). During one keynote session I proposed a continuum of data sharing, spanning from traditional server-based DAS to traditional external NAS and SAN with multiple points in between – including external DAS, simple pooled storage, advanced pooled storage, shared storage and HA (high-availability) shared storage. Each step along the continuum adds incremental features and value, giving datacenter architects the latitude to choose – and pay for – only the level of sharing absolutely required, and no more. This level of choice is being very warmly received by the market as storage requirements vary widely among Web-cloud, private cloud, traditional enterprise, and SMB configurations and applications.

Sharable DAS pools storage for operational benefits and efficiencies
Sharable DAS, with its inherent storage resource pooling, offers a number of operational benefits and efficiencies when applied at the rack level:

  • Standardized storage architectures, leveraging economies of scale of today’s high-volume DAS solutions, and minimizing storage qualifications
  • Simplified volume, boot and unified storage management by extending today’s widely deployed storage management tools
  • Reduced number of compute and storage SKUs within a datacenter, minimizing training and maintenance costs
  • Simplified life cycle management by de-coupling the upgrade cycles of compute (typically 18-24 months) and storage (typically 3-5 years)

LSI rolls out proof-of-concept Rack Scale architecture using sharable DAS
In addition to just talking about sharable DAS at AIS, we also rolled out a proof-of-concept Rack Scale architecture employing sharable DAS.  In it we configured 20 servers with 12Gb/s SAS RAID controllers, a prototype 40-port 12Gb/s SAS switch (that’s 160 12Gb/s SAS lanes) and 10 JBODs with 12Gb/s SAS for a total of 200 disk drives – all in a single rack. The drives were configured as a single storage resource pool with our media sharing (ability to spread volumes across multiple disk drives and aggregate disk drive bandwidth) and distributed RAID (ability to disperse data protection across multiple disk drives) features. This configuration pools the server storage into a single resource, delivering substantial, tangible performance and availability improvements, when compared to 20 stand-alone servers. In particular, the configuration:

  • Enables active servers to claim unused bandwidth and IOPs
  • Enhances server performance when a disk drive fails, providing consistent high performance to applications by distributing the impact of a single drive failure across all the drives in the pool
  • Accelerates time to redundancy (TTR), greatly minimizing the window of vulnerability for subsequent disk drive failures

I’m sure you’ll agree with me that Rack Scale architecture with sharable DAS is clearly a major step forward in providing a wide range of storage solutions under a single architecture. This in turn provides a multitude of operational efficiencies and performance benefits, giving datacenter architects wide latitude to employ what is needed – and only what is needed.

Now that we’ve tackled the #1 item on the kindergarten learning list, maybe I’ll set my sights on another item, like “Take a nap every afternoon.”



Gerry Smith leads the architectural definition of future products, including silicon, firmware and software for LSI’s industry-leading I/O controller and MegaRAID product lines as vice president of architecture for the RAID Storage Division at LSI.... Read more

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4 comments on “AIS: All I really need to know I learned in kindergarten (… think sharing)

    • Thanks for your question. Our AIS demonstration was a “proof of concept” demo intended to spark dialogue and discussion relative to the value propositions provided by the solution and solicit feedback for eventual product specifications. We are scoping the initial solution as a single cabinet that supports in the neighborhood of 240 drives. The final number will be highly dependent on the type and density of the JBOD disk enclosures and the number of servers in the configuration. Also, please keep in mind that the architecture is intended to support SATA drives as well. Planning is underway to finalize both the product requirements and specifications, as well as the target release date. We’ll provide more details as they’re available.

  1. In my humble opinion, 240 drives limit is at least 5 times too low for a 40 4x port SAS3 (12Gbs) switch given that:

    1) Its overall bandwidth is 40x4x12/8=240GB/sec, out of which 120GB/sec should be available to JBODs.
    2) It’s possible to put at least 600 3.5″ drives/rack (using Quanta M4600H or similar 4U drive enclosures) or many more 2.5″ drives.
    3) Unless using only SSD drives, having a limit of 240 drives per switch (which is already exceeded by an immediately available and I guess much cheaper SAS6160 switch) will mean a giant waste of available switch bandwith.

    My vote (for what it’s worth) is for it to support of at least 1,200 drives (but 2,000 would be even better).

    • Thanks for the great follow-up question. You are correct relative to the performance capability that’s possible to achieve by the architecture. Please note the initial answer was based on the first-out solution being focused on a single cabinet and providing a proper balance between the number of servers, number of JBODs and number of drives that are physically able to be provided in a single cabinet. We intend to support multiple racks with much greater scale (possibly up to the extent you’re suggesting) with subsequent releases.

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