2.5 inch 10K RPM Drives - The New Model of Efficiency

Posted by Anthony Sayre, Strategic Alliance Manager
November 9, 2011

With the help of our consultants, many of our storage clients are moving their modular disk standard to 2.5” 10K rpm speed SAS disk for their high-performance mission critical data storage solutions. We highly recommend to our clients to make this switch if they have not already.

Why would anyone intentionally move to a 10K rpm speed drives over 15K rpm? Especially for mission critical apps? A little analytics gives us the answer.

The key differentiators boil down to density and price. These two attributes work together to overcome the IOPS delta between 10K rpm vs. 15K rpm and here’s the secret sauce:

1) Density - 24 x 2.5” 10K rpm SAS drives fit into a 2U disk shelf, which makes it denser than regular 3U disk and even the so-called “hi-density” 4U shelf which HDS also offers.

2) Price - The individual drive and shelf price for 2.5” 10K are the same as that of the regular 3.5” 15K drive and shelf, and about a 3rd the cost of one hi-density shelf. But since 24 can fit into one 2U tray instead of 15 in a 3U tray (or even 38 in a 4U tray) the overall cost per tray is less. With the lowest cost available for SAS disk from Hitachi Data Systems (HDS), clients can easily afford to add a few more disks to make up the IOPS difference and still save money.

The following chart illustrates how this works:

  • Each row in the above chart represents one full tray’s worth of disk for each disk type. The top section compares IOPS per tray, IOPS per rack unit, etc… while the bottom section compares environmentals
  • The “IOPS/tray” column shows numbers that favor the 3.5” hi-density 600GB option. But since the 2.5” option is 2U instead of 4U, the “Computed IOPS/Rack Unit” column levels the playing field. And since the cost is less per tray, the “IOPS/dollar” is also about even. The “Raw GB/$” is quite a bit better for the upstart 2.5” 10K drive.
  • The environmental comparison is off-the-charts in favor of the 2.5” 10K. For those that have power cooling cost concerns, this is the option to go with.

What does this mean in plain terms?
We are working on a solution currently where the client asked for an AMS2500 with about 87TB usable for a hi-performance production environment. We configured a 600GB 3.5” 15K “hi-density” version as well as a 600GB 2.5” 10K version. The 2.5” 10K MSRP hardware total came to $480K while the 3.5” “hi-density” version MSRP total came to $629K, 23%(!) higher.

The total IOPS for the 2.5” 10K version is 8%-10% less than the “hi-density” version, so the IOPS delta is negligible. And since the cost is so much less, we could add more drives into the data storage solution to make up the IOPS difference while still remaining at or below the cost of the “hi-density” solution (which would also increase the usable capacity).

It’s also interesting to note the 2.5” 10K version takes up a total of 22 rack units while the so-called “hi-density” version takes up 28 rack units. Lastly, the power/cooling numbers are 46%+ less (!) in the 2.5” 10K version. Remember this is just an 87TB usable solution and the argument is compelling. It becomes even more compelling as the total capacity goes up.

This is why several of ASG’s largest HDS clients are making the switch now to 2.5” 10K rpm drives as a standard for production or are seriously considering it.

Steve Wine, our most senior account executive based out of our Denver, Colorado office summed it up:

"We presented these drive performance numbers to my largest storage client in Colorado and it convinced them to make the switch. They deliver cloud storage and other related services so the need for high-performance was paramount and we took that into consideration. We now have several AMS units installed (at the client) with all 2.5” drives and they are performing perfectly, even in their highest performance tier.  Because they buy so much disk storage, switching to 2.5” drives has been a huge cost savings both on cap ex and op ex side. This will be their standard for most modular storage going forward."

The complete analysis has garnered a lot of great feedback from our clients who really use it for data center planning. For a copy of this analysis containing a complete Hitachi modular drive comparison chart containing all available options, contact Anthony Sayre at "asayre (at) virtual.com".

About the Author
Anthony Sayre
ASG Advanced Product Specialist
asayre (at) virtual.com

About Anthony Sayre Anthony Sayre is a Strategic Alliance Manager at ASG and our resident expert for Hitachi Data Systems and Brocade solutions. Within a mere five years, Anthony has helped make ASG one of Hitachi’s top commercial partners. Today, ASG has the highest level of certifications of any other Hitachi VAR nationwide.

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