Shu Jiwu

Storage Virtualization Based Asynchronous Remote Mirror

Computerized data becomes more and more critical in today’s digital life. With the help of redundant hardware and software, remote mirror can keep information systems alive by seamless service switching, even encountering site corruptions. Unfortunately, existing mirror systems have some limitations such as restrictions to specific storage devices and/or low level drivers. In this paper, we design a storage virtualization based asynchronous remote mirror system, named as SVAM (Storage Virtualization based Asynchronous Mirror). First, SVAM utilizes a logical volume structure, AMLV (Asynchronous Mirror Logic Volume), to provide data protection and make it the basic data container. This way, there is no device and driver dependency at all. Secondly, we present a server free mechanism to offload mirror related jobs to SAN IO nodes, therefore good performance can be expected. Finally, SVAM incorporates an advanced mirror protocol to support seamless service switching while keeping low network bandwidth overhead. Experiments and evaluation results demonstrate that SVAM has the ability to provide high reliability while only introduce little overhead: tolerated a site corruption while kept providing service, the cost was only 12.3% more time.

A new numerical method on American option pricing

Mathematically, the Black-Scholes model of American option pricing is a free boundary problem of partial differential equation. It is well known that this model is a nonlinear problem, and it has no closed form solution. We can only obtain an approximate solution by numerical method, but the precision and stability are hard to control, because the singularity at the exercise boundary near expiration date has a great effect on precision and stability for numerical method. We propose a new numerical method, FDA method, to solve the American option pricing problem, which combines advantages the Semi-Analytical Method and the Front-Fixed Difference Method. Using the FDA method overcomes the difficulty resulting from the singularity at the terminal of optimal exercise boundary. A large amount of calculation shows that the FDA method is more accurate and stable than other numerical methods.

Design and Implementation of an Efficient Multi-version File System

The benefit of multi-version file system is high reliability. File versioning can be used for file-oriented recovery from deletion and limiting exposure to data losses during file system failure. The problem is that accesses to versions in the distant past may be prohibitively expensive. We adopt the hierarchical architecture in version space to reduce the time spent on search; We present a new structure named red black tree embedded in inode to organize versions of a directory and another new structure named red black tree with weight and link to build index for versions of a file. Using aforementioned technologies, we implement an efficient multi-version file system named thvfs. The experiment results show that the average time of searching old versions in thvfs is 34.4% lower than that in ext3cow, the famous multi-version file system.

Parallel computing for lattice Monte Carlo simulation of large-scale thin film growth

This paper proposes two viable computing strategies for distributed parallel systems: domain division with sub-domain overlapping and asynchronous communication. We have implemented a parallel computing procedure for simulation of Ti thin film growing process of a system with 1000 × 1000 atoms by means of the Monte Carlo (MC) method. This approach greatly reduces the computation time for simulation of large-scale thin film growth under realistic deposition rates. The multi-lattice MC model of deposition comprises two basic events: deposition, and surface diffusion. Since diffusion constitutes more than 90% of the total simulation time of the whole deposition process at high temperature, we concentrated on implementing a new parallel diffusion simulation that reduces communication time during simulation. Asynchronous communication and domain overlapping techniques are used to reduce the waiting time and communication time among parallel processors. The parallel algorithms we propose can simulate the thin film growth of a system with many more particles than before under realistic deposition rates, and can provide a more efficient means for computer simulation of thin film growth.