Search results for "Operating system"
showing 10 items of 134 documents
An Alternative Derivation of Johannisson's Regular Perturbation Model
2012
We provide here an alternative derivation of the generalization of the nonlinear Turin model for dispersion unmanaged coherent optical links provided in Johannisson's report [arXiv:1205.2193]
GekkoFS - A Temporary Distributed File System for HPC Applications
2018
We present GekkoFS, a temporary, highly-scalable burst buffer file system which has been specifically optimized for new access patterns of data-intensive High-Performance Computing (HPC) applications. The file system provides relaxed POSIX semantics, only offering features which are actually required by most (not all) applications. It is able to provide scalable I/O performance and reaches millions of metadata operations already for a small number of nodes, significantly outperforming the capabilities of general-purpose parallel file systems. The work has been funded by the German Research Foundation (DFG) through the ADA-FS project as part of the Priority Programme 1648. It is also support…
LPCC
2019
Most high-performance computing (HPC) clusters use a global parallel file system to enable high data throughput. The parallel file system is typically centralized and its storage media are physically separated from the compute cluster. Compute nodes as clients of the parallel file system are often additionally equipped with SSDs. The node internal storage media are rarely well-integrated into the I/O and compute workflows. How to make full and flexible use of these storage media is therefore a valuable research question. In this paper, we propose a hierarchical Persistent Client Caching (LPCC) mechanism for the Lustre file system. LPCC provides two modes: RW-PCC builds a read-write cache on…
A configurable rule based classful token bucket filter network request scheduler for the lustre file system
2017
HPC file systems today work in a best-effort manner where individual applications can flood the file system with requests, effectively leading to a denial of service for all other tasks. This paper presents a classful Token Bucket Filter (TBF) policy for the Lustre file system. The TBF enforces Remote Procedure Call (RPC) rate limitations based on (potentially complex) Quality of Service (QoS) rules. The QoS rules are enforced in Lustre's Object Storage Servers, where each request is assigned to an automatically created QoS class.The proposed QoS implementation for Lustre enables various features for each class including the support for high-priority and real-time requests even under heavy …
Direct lookup and hash-based metadata placement for local file systems
2013
New challenges to file systems' metadata performance are imposed by the continuously growing number of files existing in file systems. The total amount of metadata can become too big to be cached, potentially leading to multiple storage device accesses for a single metadata lookup operation. This paper takes a look at the limitations of traditional file system designs and discusses an alternative metadata handling approach, using hash-based concepts already established for metadata and data placement in distributed storage systems. Furthermore, a POSIX compliant prototype implementation based on these concepts is introduced and benchmarked. A variety of file system metadata and data operati…
MERCURY: A Transparent Guided I/O Framework for High Performance I/O Stacks
2017
The performance gap between processors and I/O represents a serious scalability limitation for applications running on computing clusters. Parallel file systems often provide mechanisms that allow programmers to disclose their I/O pattern knowledge to the lower layers of the I/O stack through a hints API. This information can be used by the file system to boost the application performance. Unfortunately, programmers rarely make use of these features, missing the opportunity to exploit the full potential of the storage system. In this paper we propose MERCURY, a transparent guided I/O framework able to optimize file I/O patterns in scientific applications, allowing users to control the I/O b…
ESB: Ext2 Split Block Device
2012
Solid State Disks (SSDs) start to replace rotating media (hard disks, HDD) in many areas, but are still not as cost efficient concerning capacity to completely replace them. One approach to use their superior performance properties is to use them as a cache for magnetic disks to speed up overall storage operations. In this paper, we present and evaluate a file system level optimization based on ext2. We split metadata and data and store the metadata on a SDD while the data remains on a common HDD. We evaluate our system with filebench under a file server, web server, and web proxy scenario and compare the results with flashcache. We find that many of the scenarios do not contain enough meta…
Usability analysis of a novel biometric authentication approach for android-based mobile devices
2014
Mobile devices are widely replacing the standard personal computers thanks to their small size and user-friendly use. As a consequence, the amount of information, often confidential, exchanged through these devices is raising. This makes them potential targets of malicious network hackers. The use of simple passwords or PIN are not sufficient to provide a suitable security level for those applications requiring high protection levels on data and services. In this paper a biometric authentication system, as a running Android application, has been developed and implemented on a real mobile device. A system test on real users has been also carried out in order to evaluate the human-machine int…
Reverse and normal drag along a fault
2005
An analysis of the theoretical displacement field around a single dip-slip fault at depth reveals that normal and reverse fault drag develop by perturbation flow induced by fault slip. We analytically model the heterogeneous part of the instantaneous displacement field of an isolated two-dimensional mode II fault in an infinite, homogeneous elastic body in response to fault slip. Material on both sides of the fault is displaced and ‘opposing circulation cells’ arise on opposite sides of the fault, with displacement magnitudes increasing towards the center of the fault. Both normal and reverse drag can develop at the fault center depending on the angle between the markers and the fault; norm…
Computer-aided calculation of the molecular size of nondenatured proteins in pore-gradient gel electrophoresis
1991
A computer program written in Turbo C is described, which uses the two-step mathematical procedure published recently (Rothe, G. M., Electrophoresis 1988, 9, 307-316) to evaluate the molecular mass, Stokes' radius, spherical radius, and frictional coefficient of nondenatured proteins. The program runs on any IBM-PC or 100% compatible IBM-PC, provided the disk operating system MS-DOS or PC-DOS 3.0 or later has been installed. Functions that are permanently in use are accessible by menu. Storage and loading of data from disk and help instructions can be called by use of function keys. The program provides several tables into which inserted and calculated data is automatically integrated. Each…