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ÐEfficient and effective buffering of disk blocks in main memory is critical for better file system performance due to a wide speed gap between main memory and hard disks. In such a buffering system, one of the most important design decisions is the block replacement policy that determines which disk block to replace when the buffer is full. In this paper,(More)
The performance of face recognition methods using subspace projection is directly related to the characteristics of their basis images, especially in the cases of local distortion or partial occlusion. In order for a subspace projection method to be robust to local distortion and partial occlusion, the basis images generated by the method should exhibit a(More)
Two contributions are made in this paper. First, we show that system level characterization of file block references is inadequate for maximizing buffer cache performance. We show that a finer-grained characterization approach is needed. Though application level characterization methods have been proposed, this is the first attempt, to the best of our(More)
Sam H. Nohs Sang Lyul Mint t Department of Computer Engineering Seoul National University Seoul 151-742, Korea http://ssrnet.snu.ac.kr http://archi.snu.ac.kr We show that there exists a spectrum of block replacement policies that subsumes both the Least Recently Used (LRU) and the Least Frequently Used (LFU) policies. The spectrum is formed according to how(More)
In embedded systems and laptops, flash memory storage such as SSDs (Solid State Drive) have been gaining popularity due to its low energy consumption and durability. As SSDs are flash memory based devices, their performance behavior differs from those of magnetic disks. However, little attention has been paid on how to exploit SSDs from the disk scheduling(More)
Hybrid storage solutions use NAND flash memory based Solid State Drives (SSDs) as non-volatile cache and traditional Hard Disk Drives (HDDs) as lower level storage. Unlike a typical cache, internally, the flash memory cache is divided into cache space and over-provisioned space, used for garbage collection. We show that balancing the two spaces(More)
In this paper, we propose a new adaptive bu er management scheme called DEAR (DEtection based Adaptive Replacement) that automatically detects the block reference patterns of applications and applies di erent replacement policies to di erent applications based on the detected reference pattern. The proposed DEAR scheme uses a periodic process. Detection is(More)
In this paper, we present a virtual machine based SSD Simulator, VSSIM (Virtual SSD Simulator). VSSIM intends to address the issues of the trace driven simulation, e.g. trace re-scaling, accurate replay, etc. VSSIM operates on top of QEMU/KVM with software based SSD module. VSSIM runs in realtime and allows the user to measure both the host performance and(More)
While the move from SLC to MLC/TLC flash memory technology is increasing SSD capacity at lower cost, it is being done at the cost of sacrificing reliability. An approach to remedy this loss is to employ the RAID architecture with the chips that comprise SSDs. However, using the traditional RAID approach may result in negative effects as the total number of(More)
Non-volatile RAM (NVRAM) such as PRAM (Phase-change RAM), FeRAM (Ferroelectric RAM), and MRAM (Magnetoresistive RAM) has characteristics of both non-volatile storage and random access memory (RAM). These forms of NVRAM are currently being developed by major semiconductor companies and are expected to be an everyday component in the near future. The advent(More)