— Storage Horizons Blog —

Steve Sicola

Hybrid and SSD Arrays

  • What are they good for and what are they not?
  • What are enterprise hybrids?
  • What are just SANs in a can for SMB doing HSM/ILM?!
  • What about All SSD arrays?
  • Are they worth it?

All HDD Arrays, Hybrids, and all SSD Arrays:  An Introduction

All HDD arrays are still the mainstay of the world today, but that may be changing, in the future, as SSDs come down some in price and the world’s demand, for quick business decisions, increases.

HDD arrays, such as the original ISE-1 and now the ISE-2, provide multiples of performance, over traditional arrays, with the best price/performance and lowest Total Cost of Ownership (TCO) on earth.  This has been proven, time and again, all over the world and in real benchmarks. Our focus is on the fundamentals of storage that have been ignored for 20+ years! The industry has ignored them but, at
X-IO, we strive for performance across all the capacity, reliability that is 100x over all others, half the power, and half (or less) the rack space, and acquisition costs that are competitive with any mainstream enterprise storage solution!

The hype of all-SSD arrays has really been the focus of the media today, but are the benefits real and the TCO really less? I believe that in some cases it is, but the number of use cases is small. Why? There are many reasons.

If SSD were the same price as HDD, then I’d be all over SSD because of its overall speed advantage. However, that’s not the case, so then, why all SSD in many companies? Enterprise SSD is 10-20x the $/GB of enterprise or nearline HDD. These prices will not converge anytime soon. Enterprise HDD will also come down in price which will keep the delta, between the technologies, significant.

The wild thing is that some all-SSD vendors are playing in the space where they should—high-end niches of trading floor applications. The problem is that many start-ups are trying to play in the basic enterprise where multi-application, high-capacity, and consistent I/O performance is required, not to mention where availability and reliability is needed. The numbers just are not there when it comes to cost, let alone TCO, when power, space, etc. are factored in.

When it comes to overcoming the TCO argument, some all-SSD vendors have added more “features” to be able to claim that their $/GB is the same or better than HDD. They do so by adding features, such as deduplication and compression. However, these features come with a price tag. The cost is for very high-powered servers to run the array, which drives up cost, but really drives up power! And the sheer usage of these features drives the application performance down, even with a bunch of SSD. The end result is dubious to the user, because most tier one applications either have dedupe or compression built in, or they just don’t need them, because there is not that much dedupe required.

The other aspect of adding such features to an all-SSD or tier one array is that of complexity. The complexity of the software goes up by magnitudes, driving the reliability of the software down, while also slowing down the system even further. There is no free lunch; but in this world of marketing, when ideas such as these keep on coming, good storage that is always available, gives consistent good performance, and is averse to service, is the key to all IT managers, in the end.

I believe, at this point in time, deduplication and compression are for data at rest, which is for backups and archived data. Performing these operations on tier one applications seems like a waste because it always depends on the application. But when the data is at rest, these features are in their perfect environment. Performance is not an issue here, and cost savings (by driving down capacity, currently used to free up for more data at rest) IS!

In the end, my thoughts on all-SSD arrays, today, go like this:

  • If SSD was the price of enterprise HDD and supply was able to meet demand . . .
  • And then if applications could use all the IOPS . . .
  • Then SSD will replace HDD.

Until then, all-SSD arrays are either a niche or a shill on TCO with dubious value, in most cases.

So going forward, I’m going to leave SSD arrays for now and talk about tiering and hybrid arrays, as to me, they offer the most benefit, for years to come, in both price/performance and overall TCO reduction.

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