FSCQ is a file system with a machine-checkable proof (using the Coq proof assistant [2]) that its implementation meets its specification, even under crashes. FSCQ provably avoids bugs that have plagued previous file systems, such as performing disk writes without sufficient barriers or forgetting to zero out directory blocks. FSCQ built upon the Crash Hoare Logic (CHL) infrastructure. FSCQ uses...

This paper presents an optimization mechanism to increase the performance of cloud services that transfer groups of deduplicated virtual machine (VM) images. This is necessary as the naive data transfer approach for groups of deduplicated VM images is extremely inefficient as it generates highly random disk access pattern. The optimization mechanism presented significantly improves the VM image...

Abstract. In an IaaS (Infrastructure-as-a-Service) cloud services, storage needs of VM (Virtual Machine) instances are met through virtual disks (i.e. virtual block devices). However, it is nontrivial to provide virtual disks to VMs in an efficient and scalable way for a couple of reasons. First, a VM host may be required to provide virtual disks for a large number of VMs. It is difficult to as...

Flat Datacenter Storage (FDS) is a high-performance, fault-tolerant, large-scale, locality-oblivious blob store. Using a novel combination of full bisection bandwidth networks, data and metadata striping, and flow control, FDS multiplexes an application’s large-scale I/O across the available throughput and latency budget of every disk in a cluster. FDS therefore makes many optimizations around ...

Abstract—The scattering of an arbitrary electromagnetic wave by a thin disk located in free space is formulated rigorously in terms of coupled dual integral equations (CDIEs) for the unknown images of the jumps and average values of the normal to the disk scattered-field components. Considered are three cases of the disk: (1) Zero-thickness perfectly electrically conducting (PEC) disk, (2) thin...

In this paper, perturbations of an accretion disk by a star orbiting around a black hole are studied. We report on a numerical experiment, which has been carried out by using a parallel-machine code originally developed by Dönmez (2004). An initially steady state accretion disk near a non-rotating (Schwarzschild) black hole interacts with a ”star”, modeled as an initially circular region of inc...

Abstract The Milky Way disk consists of two prominent components—a thick, alpha-rich, low-metallicity component and a thin, metal-rich, low-alpha component. External galaxies have been shown to contain thin- thick-disk components, but whether distinct components in the [ α /Fe]–[Z/H] plane exist other Way-like is not yet known. We present Very Large Telescope (VLT)—Multi Unit Spectroscopic Expl...

The membrane surfaces within the rod outer segment of the toad, Bufo marinus, were exposed by rapid-freezing followed by freeze-fracture and deep-etching. Platinum-carbon replicas of disk membranes prepared in this way demonstrate a distinct sidedness. The membrane surface that faces the lumen of the disk shows a fine granularity; particles of approximately 6 nm are packed at a density of appro...

We analyze the relationship between the mass of a spherical component and the minimum possible thickness of stable stellar disks. This relationship for real galaxies allows the lower limit on the dark halo mass to be estimated (the thinner the stable stellar disk is, the more massive the dark halo must be). In our analysis, we use both theoretical relations and numerical N-body simulations of t...