When we suggest that a company consider an all-flash storage system to solve a performance problem, there is almost always resistance to the cost. That is a fair concern -- it's common knowledge that flash storage is more expensive than hard disk storage. But this is only true when compared device to device. When they compare the cost against the full benefit of the system, we have seen many data centers become believers and actually save money by going with a flash appliance.

The first thing to realize is that few if any flash array or flash appliance vendors really expect you to replace all of your storage with flash. And as we will discuss in our upcoming webinar, "SSD on a Budget," when used to augment existing storage, an all-flash system can be had for well under $100,000.

Many all-flash vendors will try to steer the conversation away from cost per GB to cost per input/output operations per second (IOP) -- a good strategy for vendors given the tremendous advantage that flash systems have in IOPS. If you have an application, such as a database, that is specifically IOPS constrained then this might catch your attention.

[ Want more on how flash storage has advanced? Read Flash Storage: Ready For Writes. ]

The traditional way of dealing with a storage performance problem is to create very high-drive-count arrays. The challenge with this approach, of course, is the sheer cost of deploying 100-plus hard drives to generate the right amount of performance. In addition, many data centers will only format the outer edges of those drives to make sure that data is landing on the fastest portion of the drive. This technique obviously wastes even more capacity and consumes even more power and budget dollars.

All-flash arrays and appliances eliminate the high drive count array problem by moving the applications data to a high-performance, low-latency storage area that actually ends up being less expensive, requires less power and provides better performance. But this scenario is the low hanging fruit for an all-flash return on investment (ROI).

Where all-flash systems can make a real difference to the broader set of data center applications is in virtual desktop or virtual server environments to increase virtual machine density. High VM-count physical servers create a lot of random storage input/output traffic, a traffic pattern that memory-based storage is well able to handle. As we discussed in our article "Optimize The Storage Infrastructure For Increased VM Density," flash storage systems are ideally suited to solve the performance challenges caused by dense environments; RAM, storage network I/O and storage device latency.

The real value is that flash solves these problems to enable a dense VM-to-host ratio. As a result, the ROI becomes more than just how many hard drives you can replace. Instead, all-flash systems enable the creation of extremely dense virtual server environments that eliminate many of the physical server hosts that would be required. Because these hosts can start at $16,000 and cost well over $50,000, the elimination of as few as two or three can easily pay for the all-flash investment.

Server and desktop virtualization, though, are not the only places that an all-flash investment can easily pay for itself. Databases, as mentioned, also can benefit from the implementation of this type of device. By putting the entire database, not just hot files, on flash the number of users can be increased significantly. This again eliminates some of the additional database host servers that would be required to keep application response time acceptable to users.

Finally, a database environment that leverages all-flash can also respond more quickly to large batch processing requests such as analytical reports. The end result would mean greater and more rapid decision-support capabilities derived from the goldmine housed within databases. The ROI of flash is essentially all about density. How many more virtual machines can be supported, and how many more users can be supported on a per-host basis? Although the elimination of unneeded hard drives is important and certainly can save power, the elimination of unneeded hosts can save even more dollars and potentially even more power.

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