Wikibon’s own David Floyer has written an incredibly detailed article entitled Hybrid Storage Poised to Disrupt Traditional Disk Arrays. This article details a comprehensive baseline which:
- Provides a common definition of what constitutes hybrid storage,
- Provides detailed cost comparisons that explain why true hybrid storage system are ultimately less expensive than their traditional storage brethren as the need for more IOPS grows,
- Explains the architecture that comprises hybrid storage systems, and,
- Identifies the point at which hybrid storage becomes the cost leader.
The cost/performance factor
For CIOs, ensuring that the storage selection meets operational workload needs at a reasonable cost is of paramount concern, particularly since storage can often consume a not insignificant percentage of the IT budget. For many CIOs, storage capacity has become an almost secondary concern. Certain workloads are able to leverage modern array features such as deduplication and compression technologies to great effect, thus reducing the need to worry as much about capacity as was necessary in the past. For example, VDI workloads, because of the great similarity in the virtual machines that make up the solution, can often achieve 75% or higher data reduction rates in production, practically solving the capacity issue.
So, for CIOs, the great storage capacity expansion question is easing, if only a little bit.
However, storage performance demands for modern workloads have emerged as the next great challenge. Historical workloads in mainstream IT shops have been able to rely on spinning disks to provide enough IOPS to meet workload needs, at least with the right planning. Organizations could choose from low IOPS 7200 RPM SATA disks or 15K RPM SAS disks, which provide about double the IOPS of the SATA disks. As workloads demanded more performance, CIOs could simply add more spinning disks, generally in the form of another disk shelf.
Capacity and performance decoupled
That was OK when capacity growth and performance demand were growing as one. Adding more disks both increased overall capacity and added more IOPS to the storage pool.
However, while capacity growth is still happening, modern workloads are much more IOPS hungry than has been seen in the past in mainstream IT. Further, storage performance woes are no longer visible to just IT. Consider VDI initiatives. If VDI is implemented in an organization with the wrong storage, the end result is directly experienced by frustrated users who become subjected to boot and login storms, which come to life when storage cannot keep up with demand in such situations.
Without a change in storage buying options, CIOs would be forced to buy more and more disks just to meet performance demands. We have seen organizations take drastic steps, such as short stroking, to meet performance demands, even though such techniques had a negative impact on capacity. So CIOs were seeing hand-in-hand capacity and performance increases happening at different rates, thus requiring strategies to balance the two needs while still attempting to balance the economics of the overall solution.
In order to improve performance, some vendors began adding flash-based storage to traditional storage systems and using these drives as a sort of cache in front of the hard disk. However, as David explains in his article, this has not always been the best option.
A solution emerges
As you might guess from the title of David’s article, hybrid storage solutions have emerged as the sweet spot for many modern mainstream workloads. Although IT shops still have to meet capacity needs, modern hybrid storage arrays generally provide adequate capacity and, when coupled with a variety of data reduction features – deduplication and compression – capacity needs can be easily met. Where hybrid storage arrays truly shine for CIOs is on the performance side of the equation.
For comparative purposes, a true hybrid solution is defined as one that takes a flash-first approach to data storage. I won’t repeat here the full text, but refer to the VM-aware Hybrid Definition section in David’s article for more information.
Evaluating Hybrid Suppliers
In his research for his article, David spoke with customers of several vendors. The methodology laid out in his article is geared to help customers evaluate important criteria of available solutions. The table below outlines how Tintri stacks up to the three primary characteristics that David outlined as being necessary for an offering to be considered a true hybrid solution.
|The IO queues for each virtual machine are fully reflected and managed in both the hypervisor and the storage array, with a single point of control for any change of priority.||Tintri provides complete end-to-end tracking and visualization of performance from both the hypervisor down and from the storage layer up, ensuring that administrators are able to procure critical statistics from whatever tool is in use. The goal is to ensure that storage performance remains at acceptable levels and reduces write latency.|
|All data is initially written to flash (flash-first).||Tintri’s solution takes a flash-first approach by ensuring that all data written to the storage array is initially written to high performance flash storage before being offloaded to slower rotational storage. This results in much higher levels of throughput, which is one of the key differentiators between hybrid storage and traditional arrays.|
|Virtual machine storage objects are mapped directly to objects held in the storage array.||Tintri VMstore feature is VM-aware associates the storage array directly to the virtual machines and critical business applications.|
David goes into great depth and demonstrates the point at which a hybrid storage array begins to outshine traditional storage arrays from a cost/IOPS perspective. In his analysis, David uses a scenario that requires 10 TB of usable capacity and demonstrates that, at the 7,000 IOPS mark, a hybrid system and a traditional disk system have about the same price from a performance perspective. Beyond that mark, the cost of the traditional disk system continues to escalate as spindles are added to continue growing performance while the hybrid continues to have plenty of excess IOPS capacity to meet continuing needs.
For a CIO, perhaps the most critical and succinct part of the analysis is as follows:
- An environment requiring 15,000 IOPS from 1 terabytes of usable storage would require:
- 64 drives and 1 TB of flash in a traditional storage array with a flash cache;
- 16 drives including 2.4TB of flash in a hybrid storage array;
- The traditional storage array would cost more than twice as much as the hybrid ($190,000 vs. $88,000).
Action Item: CIOs who are considering expanding storage or replacing existing storage need to carefully consider the full range of options before them with particular attention paid to true hybrid solutions that maximize both IOPS and capacity needs to provide outstanding performance for mainstream and emerging workloads. By doing so, CIOs can avoid simply throwing more spindles at older systems and achieve much better results at much lower overall costs.