Telomere: Real-Time NAND Flash Storage

Modern solid-state disks achieve high data transfer rates due to their massive internal parallelism. However, out-of-place updates for flash memory incur garbage collection costs when valid data needs to be copied during space reclamation. The root cause of this extra cost is that solid-state disks are not always able to accurately determine data lifetime and group together data that expires before the space needs to be reclaimed. Real-time systems found in autonomous vehicles, industrial control systems, and assembly-line robots store data from hundreds of sensors and often have predictable data lifetimes. These systems require guaranteed high storage bandwidth for read and write operations by mission-critical real-time tasks. In this article, we depart from the traditional block device interface to guarantee the high throughput needed to process large volumes of data. Using data lifetime information from the application layer, our proposed real-time design, called Telomere , is able to intelligently lay out data in NAND flash memory and eliminate valid page copies during garbage collection. Telomere’s real-time admission control is able to guarantee tasks their required read and write operations within their periods. Under randomly generated tasksets containing 500 tasks, Telomere achieves 30% higher throughput with a 5% storage cost compared to pre-existing techniques.

Integer Codes Correcting Asymmetric Errors in Nand Flash Memory

Memory devices based on floating-gate transistor have recently become dominant technology for non-volatile storage devices like USB flash drives, memory cards, solid-state disks, etc. In contrast to many communication channels, the errors observed in flash memory device use are not random but of special, mainly asymmetric, type. Integer codes which have proved their efficiency in many cases with asymmetric errors can be applied successfully to flash memory devices, too. This paper presents a new construction and integer codes over a ring of integers modulo A=2n+1 capable of correcting single errors of type (1,2),(±1,±2), or (1,2,3) that are typical for flash memory devices. The construction is based on the use of cyclotomic cosets of 2 modulo A. The parity-check matrices of the codes are listed for n≤10.

Accelerating I/O in ESMs using on demand filesystems

<p>Earth System Models (ESM) got much more demanding over the last years. Modelled processes got more complex and more and more processes are considered in models. In addition resolutions of the models got higher to improve accuracy of predictions. This requires faster high performance computers (HPC) and better I/O performance. One way to improve I/O performance is to use faster file systems. Last year we showed the impact of the ad-hoc file system on the performance of the ESM EMAC. An ad-hoc file system is a private parallel file system which is created on-demand for an HPC job using the node-local storage devices, in our case solid-state-disks (SSD). It only exists during the runtime of the job. Therefore output data have to be moved to a permanent file system before the job has finished. Performance improvements are due to the use of SSDs in case of small chunks of I/O or a high amount of I/O operations per second. Another reason for a performace boost is because the running job can exclusively access the file system. To get a better overview in which cases ESMs benefit from using ad-hoc file systems we repeated our performance tests with further ESMs with different I/O strategies. In total we now analyzed EMAC (parallel netcdf), ICON2.5 (netcdf with asynchronous I/O), ICON2.6 (netcdf with Climate Data Interface (CDI) library) and OpenGeoSys (parallel VTU).</p>