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Flash in the enterprise: The good, the bad, and the ugly

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We have been watching the adoption of Flash in the enterprise for over 10 years now, and we are happy to see that so much progress has been made. But why did it take so long?

One reason might be the underlying complexity of Flash technology and the underlying architectures that need to be in place to make good use of its capabilities. Reviewing these complexities can help illuminate why we have implemented the solution for caching that we have. We think we have hit on the simplest, most cost-effective use of Flash in the enterprise, but only because it takes into account the nuances of Flash technology.

The Good
First, the good part about Flash—the primary reason everyone wants to use Flash is for performance, i.e., it handles random I/O much faster than disk, and it does so at a much lower cost than that of DRAM. It is also nonvolatile, meaning it doesn’t lose data upon power loss like DRAM does, and it is extremely rugged, which is to say that mechanical vibrations don’t affect its performance.

The Bad
The “bad” part about Flash is that it is more expensive than disk, at least for now. Clearly Flash is approaching the cost per bit of the 10K and 15K RPM disk market, but when compared to 7500 RPM SATA drives, Flash is currently more expensive. The good news here is that the price of Flash is expected to continue to fall faster than that of higher-performing disks. Will its price fall faster than that of the SATA disk? No one knows, but time will tell.

But Flash is cheaper than DRAM, which is why people want to use it as a lower-cost alternative. But it is also slower than DRAM, and it is asymmetric in terms of read/write characteristics. This combination adds complexity to architectures that use Flash in the enterprise.

The Ugly
Then there is the “ugly” part of Flash. In order to write to Flash, you need to erase it first, and there are limits to the number of erases each cell can withstand. A Flash device must move and rewrite existing data to accommodate a new write request, “amplifying” the amount of data being written above the amount requested. Vendors have attempted to fix this limitation by using Flash translation layers, improved fragmentation algorithms, and advanced garbage collection and overprovisioning techniques. All these solutions have improved tremendously over the past five years, which is why we can use Flash at all in the enterprise today.

Specific Enterprise Use Cases
There are very specific enterprise use cases that are no-brainers for using Flash, despite the underlying technology limitations. Clearly, Flash should be used to take advantage of its random I/O performance advantage over disk. But ideally it should be deployed in read-dominated, random I/O workloads to minimize wear and maximize performance benefits. Plus, no one knows about the long-term data retention of Flash, as opposed to the 50-year history of disk. Using it in a read-only environment passes the headache test of worrying about long-term retention, since data protection is satisfied at a different layer. And remember, data layout matters on Flash, so avoiding small writes to the same logical location is a must.

This is why we advocate using Flash as a read cache. Read caching can make an enormous difference to application performance, only takes a small amount of Flash, and might even be the best way to use enterprise Flash today. It is at least the first thing you should try to offload performance bottlenecks—much better than the storage vendors pushing you to “just buy more disks.”

We will be discussing that in more detail in upcoming blogs, but when you add up the good, the bad, and the ugly of Flash, read caching should be considered. The risks are low, the benefits are high, and the cost is just right. Watch this space for more on this topic.

 

The post Flash in the enterprise: The good, the bad, and the ugly appeared first on Proximal Data.


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