Abstract
CERN 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.
Highlights
Every time a tape is mounted in a tape drive, the tape medium is wound around reels inside the tape drives, directly exposing the bits to the traversing drive airflow
Any airborne particles passing through the drive can be trapped between two layers of tape medium while winding the medium around reels
To make things worse the tape medium travels at high velocity within a tape drive. This means airborne particles can smash into the magnetic substrate with pressure that can cause severe physical damage to the tape
Summary
- Tape write-efficiency improvements in CASTOR S Murray, V Bahyl, G Cancio et al. - Atomic Orientation Detection using Nonlinear Optics and its Application as an Environmental Sensor M R Tawakal, H Alatas and H Hardhienata. - Tape write-efficiency improvements in CASTOR S Murray, V Bahyl, G Cancio et al. - Atomic Orientation Detection using Nonlinear Optics and its Application as an Environmental Sensor M R Tawakal, H Alatas and H Hardhienata. - Scale out databases for CERN use cases Zbigniew Baranowski, Maciej Grzybek, Luca Canali et al. CHEP IOP Conf.
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