Short latency responses in the averaged electro-oculogram elicited by vibrational impulse stimuli applied to the skull: could they reflect vestibulo-ocular reflex function?

Objectives: To investigate whether vibrational impulse stimuli applied to the skull can be used to evoke the vestibulo-ocular reflex (VOR) and detect vestibular lesions. Methods: Twenty four patients with unilateral vestibular loss (UVD), five with bilateral vestibular loss, two with ocular palsies, and 10 healthy subjects participated. Vibrations of the skull were induced with head taps and with a single period of 160 Hz tone burst on the inion, vertex, and the mastoids while the patients viewed a distant target. Several patients were also examined while viewing a near target, with eccentric gaze and in tilted postures. Responses were recorded by EOG. Results: Responses occurred between 5 ms and 20 ms and seemed to be compensatory to the second phase of the sine wave of vibration impulse and were greatly diminished/absent in patients with bilateral VD and ocular palsies. The patients with UVD had asymmetrical responses in the vertical EOG with stimuli applied on the inion and vertex, with enhancement of the response amplitude on the side of vestibular loss and/or diminution on the healthy side. The asymmetry ratios between the healthy subjects and patients with UVD, and among patients with UVD were statistically significant. Some gaze and positional influences could be demonstrated consistent with otolithic reflexes. Conclusion: If the asymmetric responses to skull vibration in UVD result from passive oscillatory movements of the orbital tissues they may reflect the otolith mediated sustained skew torsion. Conversely, if generated by active eye movements, their likely origin is a phasic VOR

An efficient, modular and simple tape archiving solution for LHC Run-3

The IT Storage group at CERN develops the software responsible for archiving to tape the custodial copy of the physics data generated by the LHC experiments. Physics run 3 will start in 2021 and will introduce two major challenges for which the tape archive software must be evolved. Firstly the software will need to make more efficient use of tape drives in order to sustain the predicted data rate of 150 petabytes per year as opposed to the current 50 petabytes per year. Secondly the software will need to be seamlessly integrated with EOS, which has become the de facto disk storage system provided by the IT Storage group for physics data. The tape storage software for LHC physics run 3 is code named CTA (the CERN Tape Archive). This paper describes how CTA will introduce a pre-emptive drive scheduler to use tape drives more efficiently, will encapsulate all tape software into a single module that will sit behind one or more EOS systems, and will be simpler by dropping support for obsolete backwards compatibility

Tape write-efficiency improvements in CASTOR

The CERN Advanced STORage manager (CASTOR) is used to archive to tape the physics data of past and present physics experiments. For reasons of physical storage space, all of the tape resident data in CASTOR are repacked onto higher density tapes approximately every two years. Improving the performance of writing files smaller than 2GB to tape is essential in order to keep the time needed to repack all of the tape resident data within a period of no more than 1 year. This paper reports on the solution to writing efficiently to tape that is currently in its early deployment phases at CERN

Tape SCSI monitoring and encryption at CERN

CERN currently manages the largest data archive in the HEP domain; over 180PB of custodial data is archived across 7 enterprise tape libraries containing more than 25,000 tapes and using over 100 tape drives. Archival storage at this scale requires a leading edge monitoring infrastructure that acquires live and lifelong metrics from the hardware in order to assess and proactively identify potential drive and media level issues. In addition, protecting the privacy of sensitive archival data is becoming increasingly important and with it the need for a scalable, compute-efficient and cost-effective solution for data encryption. In this paper, we first describe the implementation of acquiring tape medium and drive related metrics reported by the SCSI interface and its integration with our monitoring system. We then address the incorporation of tape drive real-time encryption with dedicated drive hardware into the CASTOR [1] hierarchical mass storage system

Data Center Environmental Sensor for safeguarding the CERN data archive

International audienceCERN has been archiving data on tapes in its Computer Center for decades and its archive system is now holding more than 135 PB of HEP data in its premises on high density tapes. For the last 20 years, tape areal bit density has been doubling every 30 months, closely following HEP data growth trends. During this period, bits on the tape magnetic substrate have been shrinking exponentially; today’s bits are now smaller than most airborne dust particles or even bacteria. Therefore tape media is now more sensitive to contamination from airborne dust particles that can land on the rollers, reels or heads. These can cause scratches on the tape media as it is being mounted or wound on the tape drive resulting in the loss of significant amounts of data. To mitigate this threat, CERN has prototyped and built custom environmental sensors that are hosted in the production tape libraries, sampling the same airflow as the surrounding drives. This paper will expose the problems and challenges we are facing and the solutions we developed in production to better monitor CERN Computer Center environment in tape libraries and to limit the impact of airborne particles on the LHC data