Flash data storage can beat HDD storage for any workloads

Many of you out there might think that flash storage is too expensive for non-mission critical workloads. However, this article which compares both the technologies has the potential to change your mind on this aspect.

Flash storage is often touted as the performance storage of choice in today’s data centers. This assumption is undisputedly true, whether the flash inclusion comes in the form of an SSD or vendor specific custom flash module, and is located in the server, all-flash array or hybrid array.

It is now an industry renowned fact that flash can perform up to three orders of magnitude faster than HDD storage, and has up to two orders of magnitude better reliability based on unrecoverable bit error rate. That is why flash makes complete sense when it comes to mission critical performance workloads for the vast majority of IT managers.

But what about flash based storage for primary but non-mission critical workloads? Because of its expense, there is a pervasive perception by many IT organizations that flash data storage cannot be used for non-mission critical workloads. However, based on objective reality it is not and here’s why it is so?

Cost crossover- When it comes to flash, IT managers argue that HDD storage systems using 15K/10K RPM 2.5 inches small form factor drives are less costly than SSDs. But what about the cost of storage software services, power, cooling costs, rack space, floor space, maintenance, reliability, availability and serviceability?

Thus, when all these factors are added, a clear cut picture of more realistic total cost can be represented as dollar per effective usable GB. So, when we compare flash data storage and HDD storage based on dollars per effective usable GB, the picture changes considerably.

Storage services software- Usually, storage software is bundled with flash based storage while it tends to be a separate licensed and maintenance line item for HDD storage. It is practically proven that data reduction technologies like dedup and compression do a better job on flash storage than HDD storage. This may feel a bit counterintuitive since those techs are compute-intensive; however, the metadata used in all of them is kept on the storage medium.

When it comes to latency, flash storage latency is 1000x lower than HDD storage. That means data reduction technologies in flash storage can operate in-line at maximum optimization without causing noticeable difference in application response time.

IT organizations using both types of storage have yielded an average result of three times better data reduction on flash data storage. Flash commonly averages a 6:1 data reduction rate over a variety of data — some data reduces much more than others — while the HDD storage rate averages closer to 2:1. That additional, effective usable capacity means flash storage systems require less raw storage capacity upfront. In HDDs, additional raw storage increases the storage services software licenses that are commonly tied to raw capacity.

Power and Cooling- When it comes to power and cooling costs, flash storage consumes less power and cooling resources because it has no moving parts. HDD consist platters which have to spin at a very high speed and this activity generates tremendous friction. Friction means more heat generation and so HDD based storage solutions require more cooling solutions to keep their temperatures stable at operational levels. Hence, on an average power and cooling consumption for flash-based storage ranges from 50% to 90% less per GB when compared to HDDs.

Rack and Floor Space- Obviously, SSDs have a lot of capacity cramped into 2.5 inches of form factor. So, custom flash modules have considerably more capacity than equivalent 15K/10K RPM HDDs. Thus, when it comes to rack and floor space, SSD based storage systems occupy less space than HDDs. So, those enterprise data centers which desire to have storage systems in petite form factor can go for a SSD populated storage system.

Maintenance- Flash storage requires less maintenance than HDD storage. So, investing more on flash storage do makes sense, as in future, users need not spend on maintenance costs.

Reliability and availability along with serviceability- When it comes flash based storage system, vendors offering such solutions say that these solutions are extremely reliable. So, when it comes to Uncorrectable bit rate error (UBER), Flash exhibit UBER of 10-18; that is 100 times better than the best HDD UBER of 10-16

This is due to the fact that HDDs treat an unrecoverable bit error as a failed drive. Flash drives do not. The flash drive controller treats an unrecoverable bit error as a bad cell or program erase (P/E) block and marks it as unavailable.

Revenue generators- When it comes to revenue generation, storage is an essential part of the total IT infrastructure underlying applications. Therefore, faster, more performance-consistent storage leads to faster time-to-market with development projects, Web rollouts, e-commerce and more.


In most cases, flash data storage comes in with either less than or the same dollars per effective usable GB price than 15K/10K rpm HDDs when compared in total. This is true for all-flash arrays, hybrid arrays and server-side flash.

When the revenue side of the equation is taken into account, flash storage is cheap at twice the price.

Agree or not?

Please share your comments and views on this aspect through comments section below.


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