Enmotus Blog

Intelligent Auto-tiering Balances Storage Performance, Capacity and Affordability

Posted by Adam Zagorski on Jun 22, 2015 11:10:25 AM

Back in college humanities we learned about the Inconsistent Triad. Without getting into a religious discussion, suffice it to say that the Inconsistent Triad consisted of 3 statements. Any of the 2 statements taken together were true, but the third always negated the other 2.  I bring this up because I believe we have an Inconsistent Triad in the storage business.  The 3 components of the Storage Triad are Performance, Capacity and Cost (or affordability). It is hard to get all 3!  Price_perf_cap


If you desire performance and high capacity, you need to sacrifice affordability

If you desire capacity and affordability, you need to sacrifice performance.

If you desire performance at an affordable price point, you need to sacrifice capacity

This is where hybrid storage comes into play – Hybrid storage balances Performance, Capacity and Cost.

 Lets look at the options IT managers have and then see how hybrid storage delivers on all 3 promises.

  • All Flash Storage - You can’t argue with the fact that all flash provides ultimate performance, but it comes with a cost.  If you need multiple terabytes of capacity, all flash can become cost prohibitive very quickly. You must also consider if you are paying too much for your performance.  Can your applications take advantage of millions of IOPs, or are they going wasted? Is all of your data “hot” and does it merit being stored on high priced storage?
  • All Disk Storage – Low RPM high capacity hard drives provide the lowest dollar/gigabyte for storing your data and is most likely the best solution for data at rest or infrequently accessed data. If any level of performance is required, it is not uncommon to overprovision the storage to increase spindle costs, which quickly drives cost up.  Even with enterprise class, 15K RPM drives, short stroking and overprovisioning the drives to attain the required level of performance is quite common.
  • Hybrid Storage – There are two technologies that create hybrid storage solutions: Caching and Tiering. Both combine cost effective mass storage media (typically hard drives) with high performance storage media (typically SSD).  The result is both increased performance as well as a cost effective high capacity solution, but there are some significant differences in how they achieve this.

o   Caching – In this architecture, the SSD copies the active data onto the SSD for fast retrieval. The SSD capacity is not added to the overall volume, so the overall volume size is limited to the size of the hard drives, and provides a slightly higher $/GB ratio.  As caches increase in size, the performance benefit caps out and provides a limited addition performance gain.

o   Tiering – Rather than make copies of the active data, tiering actually promotes the active data to the SSD. Since the SSD is treated as primary storage, the capacity of the SSD is additive to the volume capacity. In fact, there is no limit to the ration of SSD to hard drive, which allows IT managers to size the fast tier according to the size of the active data set and/or dollar constraints. A properly sized tier will operate at or near the performance of the SSD (fast tier) continuously. The only trade off is that there might be a slightly longer warming process than caching.  Another advantage of tiering is that it is future proof. As the price of flash continually goes down, and make it more cost effective to implement all flash, tiering can still be utilized in all flash solutions.  Fast flash can be tiered with slower more cost/capacity effective slower flash, to create the perfect balance of Performance/Capacity/Cost in all flash solutions.


In Summary, hybrid storage, and specifically hybrid storage with tiering as the underlying technology, provides the best balance of performance, capacity and cost (affordability).  While it may not satisfy 100% of all system requirements, it will most definitely be the solution of choice for most.  Find out for yourself.  Get a FREE trial

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