Heat and Vibration: Two Factors that Can Kill Your Data

Proper management of cooling and vibration can improve performance and reliability while also reducing costs.

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Vladimir_Timofeev

It's an understatement to say that managing a data center is challenging.

Data center managers are expected to do more than ever, and with less, including protecting rapidly expanding volumes of data and a growing number of applications, maintaining availability and uptime, reducing CapEx and OpEx expenses, improving space utilization, managing energy usage and costs, and more. The list goes on and on.

We believe two words can make life a lot harder (or easier), depending on how you manage them – heat and vibration.

Today, storage vendors are squeezing more storage density into each rack, and data center architects are squeezing more racks into each data center. This enables reduced TCO because data centers can reach the same capacity targets using fewer racks and data center space. The challenge is that the more storage density you pack in, the hotter it can get, and the more likely vibrations will shake things up.

While higher-density storage is a critical enabler for the Zettabyte Age, using more of it can also introduce challenges if temperatures and vibrations are not properly managed – directly affecting virtually every pain point mentioned above. And surprisingly, power and cooling costs can even cost more than the technology inside an enclosure.

How can you keep your data at an optimal temperature with minimal vibration and deliver optimal performance all at a reasonable cost? A starting point is to look at the enclosures themselves.

Is Your Storage Enclosure Optimized for Better Cooling and Vibration?

Many times, there is a lot of focus on what’s inside the system – from hard disk drives (HDDs) and solid state drives (SSDs) to CPUs and memory. And today a 4U enclosure in a rack can hold up to 1.4 petabytes (PB) of data, with a path to reach up to 2PB with new 20TB HDDs scheduled to be released later this year.

In an analogy to the human body, the components would be the internal organs that keep people alive. However, without the skin and skeleton to protect them, the internal organs would face numerous external risks. The same is true for the enclosure. The “organs” are essential, but the enclosure that houses them must ensure that everything, including cooling and energy, operates optimally, so the organs don’t fail, and data is both protected and accessible when it’s needed.

Why Temperature Matters in the Data Center

Effective cooling is today’s challenge for very dense storage enclosures. Typically, air is drawn into the box from the cold aisle in the data center. This air passes over successive rows of drives and gets warmer with each row. The drives closest to the cold aisle stay relatively cool, while those at the back can run at significantly higher temperatures. With this type of design, the fans have to run harder (and louder).

To counteract this effect, one approach is to turn up the fan speeds – but that adds noise (and vibration) and increases power consumption. In some data centers, additional blowers are added to the cold aisle end of the enclosure to help move air even faster. This results in higher power requirements, higher energy costs, higher noise levels, higher vibration, and higher temperatures, all of which can lead to performance degradation and compromised data reliability.

A New Approach to Cooling – Start with the Storage Enclosure

An alternate approach is to select a solution that divides the storage enclosure into two thermal zones, with rows of drives in the front and in the back. Western Digital’s ArcticFlow™ takes this approach (see diagram). Like traditional design, cool air is drawn into the front zone from the cold aisle, but instead of being drawn over the rear zone, the air is then ducted around the sides of the enclosure and exhausted to the hot aisle at the rear. A cool air tunnel brings cold air directly into the center of the enclosure to cool the rear zone.

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Western Digital’s ArcticFlow technology divides the storage enclosure into two thermal zones and tunnels cold air through the center to cool the drives furthest from the cold aisle.

This enables lower fan speeds to maintain cooling, resulting in less power consumption, lower noise levels, and less vibration.

In competitive testing, using this approach requires just over half of the cooling power per drive slot. To put this into perspective, using California energy costs and typical data center efficiency, the savings amount is $1,500 per enclosure over a typical 5-year system lifecycle. In a large data center with 20,000 drives, this could equate to a $300,000 savings in energy costs.

In another competitive test, 30% of the drives in a competitive enclosure that did not use this cooling approach ran at an average of 13 degrees Celsius hotter. These enclosures were likely to have 13% more drive failures over time because of operating at elevated temperatures. 

Cooling thus enables lower TCO by running data center racks at significantly lower temperatures which translates into lower energy costs and lower likelihood of failures.

Impact of Vibrations on Data

Ever seen the video where a guy in a data center shouts at a rack of hard drives to see the impact of vibration on latency? “Don’t shout at your JBODs! They don’t like it!” he exclaims.

With today’s extreme storage density in the HDDs, drive vibration control in storage enclosures is more critical than ever. The storage enclosures housing your data may determine how much drive vibration interferes with application performance. Areal density improvements include squeezing HDD tracks closer together, which makes them more susceptible to errors occurring with vibration.

What happens is that external shock and vibration can cause HDD heads to go off track, resulting in performance delays while the head resettles and waits for the correct sector to come around again for reads or writes to resume. The HDDs are smart enough to avert data corruption, sending the wrong data or writing data in the wrong place, but while the HDD head waits, latency is introduced and application performance is reduced.

Vibration can be caused by other factors as well. When other shelves in the rack are being serviced, closing the door, or even a fork lift passing by, can cause external shock and vibration. In a dense array of HDDs, adjacent drives seeking at high speed can also induce vibration into their neighbors. And, as a result of the need for cooling, fans can transmit vibration through the chassis and also through the air as sound energy. In all of these cases, vibration can lead to latency which in turn slows application performance.

As a leading manufacturer who understands the characteristics of HDDs, Western Digital’s IsoVibe™ technology offers one approach to combat vibration within a storage enclosure. Precise cuts in the baseboard act as a suspension for the drives, providing isolation from the vibration transmitted from one drive to another. Vibration-isolated fans also minimize vibration and noise transmission. Working together, IsoVibe and ArcticFlow enable lower fans speeds, which mean less vibration. This allows maintains performance across the enclosure, even when all the drives are working hard. It will also help future generation HDDs with even tighter track densities to operate in dense enclosures with minimal performance degradation.

Proactively managing vibration ensures that drive heads are less likely to be thrown off track, and therefore more likely to maintain desired performance. Competitive testing has demonstrated 60% less operational vibration when using IsoVibe technology. The combination of these innovations can lead to lower drive return rates: another analysis using ArcticFlow and IsoVibe resulted in a 62% reduction in return rates compared to the previous generation platform without these innovations using the same drive family, same vintage, and the same capacity point.

Density, Heat and Vibration – Can’t We All Just Get Along?

It can be a balancing act, but with the right strategy and tools in place, data center architects can reap the rewards of higher-density storage while fending off the threats of heat and vibration to their data. There are innovations available today that contribute to improved cooling, lower vibration, and lower power consumption that pays off directly in terms of lower utility bills and ultimately reduced carbon footprints. Understanding cooling and vibration management enables improved performance, reliability, and cost savings when designing your data center for the Zettabyte Age.

Learn more about how to manage heat and vibration in your data center.  

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