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What happened to the promise of faster flash performance?

Leah Schoeb of Evaluator Group explains how infrastructure limitations can limit flash performance when deploying solid-state storage.

IT managers are being convinced by storage vendors that solid-state flash storage will accelerate their applications by magnitudes. But after deploying solid-state storage, many see only modest performance gains or no performance improvement at all. So, what happened to the promise of faster flash performance for applications?

There are several reasons why this can happen outside of inflated product claims (this is another discussion in itself). First, solid-state storage can expose additional bottlenecks in an infrastructure (server, network, hypervisor, applications, etc.). When storage is no longer the bottleneck, other flash performance problems may become noticeable. Historically, servers, operating systems, applications and networks have been designed to communicate with the speed of hard disk drives (HDDs). When solid-state is deployed, the rest of the infrastructure may need to be retuned to support the faster speed and response time.

For example, say a new all-flash array is installed to accelerate performance for virtual desktops. But, the storage area network was designed with enough network performance to handle the performance of HDD arrays. Replacing those HDD arrays with all-flash arrays where the performance is two to 10 times faster with latencies in the microseconds (instead of HDD milliseconds) can suddenly add an unexpected load to the network -- especially if that network is a few years old. Also, the HBAs and I/O subsystem in the server may be overloaded. Both of these things can have a major impact on overall flash performance.

Another consideration can be how the infrastructure and application are architected and deployed to get the best use out of solid-state storage. For example, database files may need to be repositioned to make the best use of solid-state. In most databases, less than 10% of the data set is considered very active or "hot" data. Placing the hot data set on solid-state storage can dramatically lower storage latency and therefore lower overall transactional response times.

Finally, solid-state storage performance thrives on parallelism and lots of multiple threads. Older, single-threaded applications will show little acceleration. With all-flash arrays, a higher volume of parallelized streams will result in a larger performance boost.

When deploying solid-state storage, realize that just deploying new faster storage may not be the end of the story. This could be just the beginning for accelerating an infrastructure and/or applications. This means that the applications, servers, operating systems, hypervisors and network may have to be optimized and re-tuned, and additional hardware may have to be purchased to handle the new storage performance deployed in the infrastructure.

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This was last published in December 2014

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Don't forget that flash performance can eventually degrade if the same sectors get written to too much. Things have to get moved around.
The key point to look at here is the fact that single variables are often not the key to any optimization. SSD takes care of one bottleneck, but it often exposes others (network, virtualization, CPU, threading, etc.).
It has come a long way and the cost of storage media has gotten cheaper. Still the issues mentioned by others like degradation and other vulnerabilities may make others hesitant. I do like the fact the power consumption does extend battery life in mobile devices.