Search results for "Rating"
showing 10 items of 2021 documents
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…
New Approaches to Regulating the Activities of Rating Agencies: A Comparative Analysis
2016
Abstract Rating agencies have become an important part of the global financial landscape. Formation of credit ratings is specified by the inherent asymmetry of financial market information and general interest in the transformation of a large amount of diverse and segmented financial information in a simple and clear assessment of the credit surveillance of borrowers that is credit rating. The world financial crisis started in 2008 has again put on the agenda the question of rating assessment accuracy and the factors influencing the rating migration. The activity of rating agencies, until recently, has had little regulation, allowing rating agencies to avoid responsibility for inaccuracies …
Corporate Investment, Debt and Liquidity Choices in the Light of Financial Constraints and Hedging Needs
2015
We examine firms' simultaneous choice of investment, debt financing and liquidity in a large sample of US corporates between 1980 and 2014. We partition the sample according to the firms' financial constraints and their needs to hedge against future shortfalls in operating income. In contrast to earlier work, our joint estimation approach shows that cash flows affect the corporate decisions of unconstrained firms more strongly than those of constrained firms. Investment-cash flow sensitivities are particularly intense for unconstrained firms with high hedging needs. Investment opportunities (as proxied by Q), however, play a larger role for constrained firms with the effects being strongest…
Quantifying Structural Subsidy Values for Systemically Important Financial Institutions
2013
Abstract Claimants to Systemically Important Financial Institutions (SIFIs) would receive transfers when governments are forced into bailouts. Ex ante, this bailout expectation lowers SIFIs’ daily funding costs. The funding cost advantage reflects both the structural level of the government support and the time-varying market valuation for such a support. Based on a large worldwide sample of banks, we estimate the value of the structural subsidy, by exploiting expectations of state support embedded in credit ratings and by applying the long-run average value of the rating bonus. The value of the structural subsidy was already sizable, 60 basis points (bp), as of the end-2007, before the cri…
Operating lease decision and the impact of capitalization in a bank-oriented country
2016
ABSTRACTThis article explores the reasons why firms engage in operating leases and examines the potential impact of a change in the related accounting rules. We focus on the accounting advantage of off-balance financing, which does not affect the typical accounting-based covenants especially important in bank-oriented countries. However, we also consider other economically based arguments. Using manually collected operating lease data for Spanish listed firms, we use the constructive capitalization method to measure as-if liabilities. The results confirm that not only size and industry affect the decision but that firms closer to breaching their covenants are also more inclined to choose op…