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flash vs hybrid storage

The Enterprise Storage Wars Are On

A massive change is taking place in enterprise storage landscape. A lot of enterprise storage managers are comparing All Flash versus Hybrid storage arrays for commissioning new storage capacity or while retiring the old. All Flash Arrays (AFAs) were until recently, too expensive to be the mainstay of enterprise storage capacity. But prices are dropping quickly, and the recent jump in efficiency is bringing AFAs back into the reckoning.

A recent Gartner report forecast painted a bright future for AFAs and expected nearly 20% of traditional high-end storage arrays to be replaced by solid-state arrays by 2019.

So, Are AFAs and not Hybrids the way forward?

If you are in any way involved in enterprise storage management, you would likely know of how AFA and hybrid array vendors are unleashing Fear, uncertainty and doubt (FUD) campaigns to boost their sales. Most of these campaigns trumpet the advantages of one array and present the alternative arrays in poor light. They paint a misleading and confusing picture for the end user (enterprise storage managers).

We have been observing the goings-on for a while now and decided it was time to step in with the truth. The perfect storage array for your enterprise depends on the composition of your workloads, performance needs and pricing, in that order. They are other factors to consider, but these are the primary ones you should focus on. Before we get into a full-fledged comparison, we will touch upon the respective advantages of the two arrays briefly.

Flash arrays have a bunch of things going for them. They offer speed and latency while using less capacity and space. Organizations using AFAs will be able to save on power and space while boosting productivity and user experience.

Hybrid arrays on the other hand are best suited to variable workloads. They can offer nearly similar speed and latency metrics as AFAs at a much cheaper cost. This makes them a good choice for enterprise applications that don’t have high-performance requirements but could still use better speed and latency.

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The Way Forward: Flash or Hybrid?

Should you switch to AFAs just because prices have dropped putting them more within your enterprise IT budget? And, are AFAs the sole future of enterprise-grade arrays? Let’s find out:

Price Matters
Much has been made of the drop in prices, but the conversation revolves mostly around the $/GB costs alone. Considering the Total Cost of Ownership and $/transaction is a better way of judging the price versus performance question. The purchase price amounts to only 20% of the total cost of ownership. At first glance it may seem like Hard disk drives (HDDs) have the advantage in $/GB and flash has an edge in $/IOPS (Input/Output Operations Per Second) terms. Hybrids are the middle path. The addition of flash storage to a tune of 2-5% of total capacity of an HDD array can yield a 2X performance gain. It will only raise array price by 10-20% but doubles IOPS and reduces latency to 3-5ms levels. Most enterprises have workloads with different requirements, and this is where the $/transaction metric becomes useful.

$/transaction metric is more reflective of real business costs and can be applied to any media type making it a better metric for comparing different technologies. All-flash arrays will cost lower $/transaction in high-transaction workloads. Whereas, hybrid arrays will cost lower $/transaction in low transaction applications.

Quality of Service (QoS)
Traditionally storage performance has only factored IOPS because storage arrays couldn’t guarantee a specific QoS. Even in a hybrid array, applications may compete for flash tier leading to over-subscription of the flash tier. This will lower performance for all applications using the array. All-Flash arrays are being promoted as the solution to QoS problems in traditional and hybrid arrays. Some AFA vendors allow IOPS provision to each application on a per-volume basis with minimum, maximum and burst parameters being specified. Storage managers can use this flexibility to make dynamic adjustments and deliver performance where it’s needed.

Data Reduction
Data reduction technologies boost the efficiency of storage arrays. AFAs use technologies like data deduplication and compression to store more data per TB and reduce the price per GB significantly. Flash leverages data reduction to bring down costs to HDD levels. But the performance of data reduction technologies will differ based on the type of data being handled. Data deduplication will be suitable for VM images, files and pictures. Compression is well suited to databases but not to photos or videos. Some arrays also give you flexibility to turn-off data reduction for latency-sensitive applications.

For instance, HP claims it can reduce footprint and power consumption by around 80% through the use of data reduction technologies.

But data reduction doesn’t work in industries which have regulations against accepting de-duplicated and rehydrated data in place of the original. Given the differences in how datasets respond to data reduction tech, a good storage array should have a selection of different reduction technologies suitable to different workloads.

Other Parameters
Another important question to consider is whether the new additions (all-flash/hybrid) will interoperate with existing storage infrastructure.

Scalability and future upgrades also need to be factored in and the granularity of AFAs and hybrid arrays needs to assessed for this.

Flash technology is an exciting prospect for enterprise storage managers, but all decisions should consider I/O requirements of workloads. Flash is still expensive compared to HDDs and needs to be provisioned for your high-performance workloads. Storage managers should use workload modelling tools to assess performance requirements. The results decisions.

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