www.siemens.com/sinorix Silent Extinguishing Disruptions to hard disk drives caused by inert gas extinguishing systems ‒ analysis and measures for the safe operation of storage systems White paper September 2015 Sinorix™ Silent Extinguishing Technology provides measures designed to ensure the safe operation of storage systems before, during and after the discharge of an inert gas extinguishing system.
Content 1 Disruptions to hard disk drives caused by inert gas extinguishing systems ..................... 3 1.1 What can disrupt hard disk drives? ............................................................................... 4 1.1.1 Pressure.................................................................................................................. 4 1.1.2 Temperature ........................................................................................................... 6 1.1.3 Noise ....
1 Disruptions to hard disk drives caused by inert gas extinguishing systems Data centers are the indispensable backbone of today’s online society. The failure of a data center causes significant problems in a very short time. As a result, the most important objective in data centers is to ensure maximum availability. Data centers need to be designed, implemented and operated in such a way that availability can be guaranteed, even in the event of a fire.
1.1 What can disrupt hard disk drives? 1.1.1 Pressure The delivery of a large amount of extinguishing agent into a protected area in a short period of time generates overpressure in the room. The first question Siemens addressed was whether overpressure caused the reported disruptions to the hard disk drives (HDDs).
p[mbar] Typical pressure gradient in the room Unregulated system Pressure relief designed for max. 3 mbar Typical pressure gradient in the room Regulated system (CDT) Pressure relief designed for max.
1.1.2 Temperature The temperature drop caused by an inert gas extinguishing discharge is only a few degrees Celsius, which disappears within a few minutes. The thermal mass of a hard disk drive body will equalize this minor drop in temperature and make it insignificant for the drive’s sensitive mechanics. In addition, the temperature drop and the dry agent introduced to the room’s atmosphere do not cause any condensation except on the surface of the discharge pipe network.
Noise sensitivity of HDDs during tests Normal performance Reduced performance Temporarily out of order Dotted line = 50 percent performance when exposed to pink noise at this level in dB(Z) Figure 5: Noise sensitivity of four 1 TB nearline storage HDDs, Siemens Corporate Technology, 2009 *) LZFmax per third-octave band The figure above shows the sound level at which the performance of the HDDs was reduced by 50 percent (yellow).
1.2 Conclusion drawn from the analyzed potential disturbance variables of pressure, temperature, noise and vibration/structure-born sound It can now be established with a high degree of certainty that the faults in storage systems as a result of an inert gas extinguishing systems discharge were caused by the impact of high noise levels on the hard disk drives. Based on the knowledge acquired at Siemens, a typical noise sensitivity profile was defined for 3.5” hard disk drives for storage systems.
With the capture and evaluation of the sensitivity profiles of hard disk drives in the frequency spectrum, a maximum noise sensitivity of the hard disk drives tested has been found in the middle audible frequency range. Each hard disk drive, however, has a typical sensitivity profile with characteristic performance degradations at a specific resonance frequency and multiples thereof.
1.4 Cause analysis An IT storage system is a complex system that is optimized by manufacturers for the following key parameters: Storage capacity Performance Reliability (in normal operating conditions) Cost per capacity Exceptional events like the discharge of a gas extinguishing system are outside the scope and specification of hard disk drives and IT storage systems, but in actual practice they do have an impact on the drives’ operation.
Noise sensitivity from hard disk to data center Physical storage: head and disk assembly Disturbance: Head to track misalignment that leads to problems in properly reading/writing the information from the magnetic layer at the disk surface Possible damage: Vibration could cause head crash that scratches the disk surface Single hard disk drive Disturbance: Raw data read by the head from the disc discarded by ECC errors: disk will go offline after certain period of persistent ECC errors Possible damage
Storage system Disturbance: The storage system will basically behave in the same manner as the combination of multiple storage system chassis Possible damage: No damage expected at the storage system level Main/backup data center Disturbance: Risk of disturbance or limited service availability caused by the main-to-backup handover (which is complex per se and has limited testability) Possible damage: No damage expected at the data center level A white paper issued by Siemens September 2015 © Sie
2 Silent Extinguishing – an holistic approach After concluding that high noise levels may disrupt hard disk drives, Siemens initiated the development of the Silent Extinguishing Technology. The goal of the development process was to devise concepts that would provide the same extinguishing performance at a significantly lower noise level. 2.
2.2 Silent Nozzle The focus of all silent extinguishing concepts for inert gas extinguishing systems is the nozzle, the place where most of the discharge energy is converted to acoustic noise. Some concepts add silencers to conventional nozzles; Sinorix Silent Nozzle reduces the noise level at the source without affecting the performance (gas flow rate and distribution) of the nozzle.
Standard nozzle, unregulated Standard nozzle, CDT Sinorix Silent Nozzle, CDT Figure 10: Sound intensity and spectrum over time of different nozzle types/extinguishing systems In addition to the noise reduction properties of the Silent Nozzle, it is important to mention the much smoother diffusion of the gas into the room atmosphere. The widely diversified jet pattern consisting of many tiny jets dramatically reduces the direct noise compared to a standard nozzle.
The Sinorix Silent Nozzle is available in a variety of materials, sizes, and different discharge patterns. X: Material SDN Brass SDNS Stainless steel VdS component certification (G 314001) Y: Size S Small Nozzle orifice ∅3.0 mm-8.4 mm M Medium Nozzle orifice ∅8.6 mm-15.4 mm L Large Nozzle orifice ∅15.6 mm-20.0 mm For manufacturing reasons, the diameters of the orifice plates are graduated in 0.2 mm increments.
SDN(S)-L Hanging nozzle, radial discharge pattern 90°/120°/150°/180°/210°/240°/270° to the pipe axis Applications with the largest possible (partial) volumes SDN(S)-M-H Hanging nozzle, horizontal discharge pattern 90°/100°/110°/250°/260°/270° to the pipe axis Applications with medium (partial) volumes SDN(S)-L-H Hanging nozzle, horizontal discharge pattern 90°/100°/110°/120°/240°/250°/260°/270° to the pipe axis Applications with the largest possible (partial) volumes SDN(S)-M-SC Standing nozzle, horizont
2.2.1 Application with inert gas extinguishing systems The following sections present the total noise reduction potential of Silent Nozzle and additional measures, summarized as Silent Extinguishing.
Direct noise vs. reflected noise: standard nozzle Direct noise vs. reflected noise: Silent Nozzle Figure 12: Comparison of direct noise and reflected noise from standard nozzles and Silent Nozzle *) LZFmax per third-octave band d1) Direct noise can reach a destructive level The flow direction of a nozzle pointing directly at the equipment enclosure (for example, a storage system cabinet) can create an incredibly high noise level.
2.3 Operational precautions Figure 13: Measures to limit “stress escalation” in the event of fire a) Design measures Implementation of the Silent Extinguishing measures, including the use of an appropriate extinguishing agent, CDT systems, Silent Nozzles, a 120-second discharge time and optimal nozzle placement.
2nd fire alarm There are only a few seconds pre-warning time left during which final measures must be performed in order to limit disruption. Evacuate people from the flooding area. Optimally prepare storage systems for the impending discharge by initiating a “panic dump.” Flooding During the flooding, Silent Extinguishing prevents the sensitive IT equipment from being exposed to excessive noise levels.
LZFmax / third octave ― dB(A) ― dB(C) ― dB(HDD) ― dB(Z) Figure 14: dB (A, C, “HDD,” Z) evaluation curves White noise/pink noise White noise is noise with a constant power spectral density in a specific frequency range. White noise is perceived as noise in the higher frequency range. White noise that is limited in bandwidth is frequently used in engineering and the natural sciences. Pink noise, also referred to as 1/f noise, is noise that decreases as the frequency increases.
Why should I protect my data center with an extinguishing system? There is no question about the need for an gas extinguishing system to protect your valuable assets: The biggest risk is always the risk of fire. Siemens recommends installing an inert gas extinguishing system to protect your data center against the risk of fire.
Converting existing systems to Silent Nozzle Existing systems can be converted to Silent Nozzles if the following factors are taken into consideration: 1. Recalculation of the system: Just as with any other inert gas extinguishing system, it is necessary to calculate and implement the nozzle cross-sections on a project-specific basis. For Sinorix Silent Nozzle, the coefficients are available for the VdS calculation software for nitrogen, argon and mixtures.
3.1 Abbreviations CDT Constant Discharge Technology dB decibels EPD Electronic Data Processing ECC Error Correcting Code HDD Hard Disk Drive Hz hertz kHz kilohertz mbar millibar RAID Redundant Array of Independent Disks RT60 Reverberation time Disclaimer All statements, information and recommendations in this document are believed to be accurate but are presented without warranty of any kind, expressed or implied.
