Almost everybody has heard about the noises that hard disks make when they are about to fail or when they’re broken already. This indicates that time’s up for the drive and you either will experience data loss or have little time left to recover your precious data. As we’ve mentioned before in our blog, the safest way to react is to get professional help and let experts recover the data. Or alternatively try to do it yourself using data recovery software and risk only recovering a fraction of the data and even possibly making a further expert recovery more difficult or, in some cases, even impossible.
What most people (and even experts) don’t know is that noise doesn’t only mean that there’s a problem, but that itself can be the cause of a severe hard drive failure and therefore of data loss!
This might not be the case when you place your speaker right next to the desktop or laptop and listen to music – even though the vibrations could make the write/read head of your hard drive jump – however a fire alarm in a data centre, for example, can be the cause of problems.
This phenomenon was recognised 10 years ago (it was identified around 2007 and the reason for it was discovered in 2008) when such an incident occurred. At first experts thought that the inert gas used in modern fire extinguishing systems were the cause of the problem: when all the smoke was gone and the storage systems were checked, they found that many hard drives had failed and some of them even lost data. Upon detailed analysis, it became clear that the cause was not the gas used by the system – but rather the noise created by the fire extinguishing system, when so-called inert gas is pressed out at high speed and pressure.
Inert gas is usually a mixture of nitrogen, argon and carbon dioxide. When fire extinguishing systems using this mixture are set off, the amount of oxygen in the air is reduced to about 10 - 13.5% causing the fire to go out as the lower level of oxygen won't support combustion. Overpressure flaps are then used to limit the pressure by allowing the corresponding air volume to be displaced outside the room. Further analysis showed that the changes in pressure did not affect hard drives. Neither did the temperature drop have any significant effect. So, what then was the cause for the malfunction of the hard drives and the resulting data loss?
It was thenoise created by the extinguishing systems. Typically there are two main noise sources: firstly the alarm siren and secondly the nozzles which discharge the inert gas at very high speed and pressure. In several lab tests conducted by Siemens in 2009 and 2014 scientists found out that most hard disks experience problems when they are exposed to noises above 120 dB. Some hard disks however start experiencing problems even at 110 dB.
The microscopic tolerances inside the modern spinning hard drive can stop operating and even experience permanent failure due to loud noises. Modern hard disk drives contain up to about 250,000 data tracks per inch nowadays so in order to read and write, the element must be within ±15% of the data track spacing. In other words, since more data tracks are now located within one inch there is almost no tolerance when the read/write head is having an offset due to vibration caused by sound. This problem has become more frequent in the second half of the last decade when modern hard disks began to hit the market.
There have been documented failures in Australia, France and most recently last September (2016) when a failure took place in the main data centre of a bank located in Bucharest, Romania. The damage caused by noise in this last case was severe: customers of ING bank in the Romanian capital were not able to use their debit cards, internet banking or execute credit card transactions because a test of their fire extinguishing system went wrong. When conducting the test pressure discrepancy the fire suspension system emitted a loud noise while expelling inert gas. The bank claimed that the noise of the inert gas fire suspension system nozzles that was created reached up to 130 dB, more than enough to knock the HDD's physical components out of alignment, bringing dozens of hard drives to a halt while precious data was lost.
Experts believe that the servers were not protected enough to withhold the high frequencies caused by the nozzles when the inert gas was released in the room. The site went offline and the bank relied solely on its backup data centre, located within a couple of miles’ proximity. It took them several days to bring back the site online.
Since inert gas fire extinguishing systems are a necessity for every data centre, how can employees in charge protect themselves against a data loss? Here are some tips that could help protect hard disks against noise related failure and data loss:
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Only use and/or purchase servers and storage systems which have special noise reduction covers attached to the side walls of the racks. Several manufactures now also include special doors in their racks to reduce sharp noise
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Surround the drives in noise-proofed racks and keep the rack doors shut
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In case of a fire alarm try to muffle the siren
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Check the position of the siren and the gas nozzle locations so they do not radiate directly onto the drives
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Increase the number and decrease the spacing of suppression nozzles to decrease their sound levels.
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Use SSDs or tape for storage when possible
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Make frequent backups and when possible replicate critical data to an offsite location or a secondary data centre
Remember: even after implementing these precautions, a fire can still occur and the system can be affected. When suffering from a data loss caused by fire, water or noise, it is better to seek special help from a professional data recovery expert, who has in-depth knowledge of what to do (and what not) after such an incident. Sometimes the system can seem unaffected, but smoke or other harmful particles could have gotten inside the rack or the hard disks and cause problems which might not be obvious initially.
More information:
Data center Server Data Recovery
Damaged Device Data Recovery
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