The Experts below are selected from a list of 9 Experts worldwide ranked by ideXlab platform

Thomas Papadakis - One of the best experts on this subject based on the ideXlab platform.

  • Continuous Data Block Placement in and Elevation from Tertiary Storage in Hierarchical Storage Servers
    Cluster Computing, 2001
    Co-Authors: Peter Triantafillou, Thomas Papadakis
    Abstract:

    Given the cost of memories and the very large Storage and bandwidth requirements of large-scale multimedia databases, hierarchical Storage servers (which consist of disk-based Secondary Storage and tape-library-based tertiary Storage) are becoming increasingly popular. Such server applications rely upon tape libraries to store all media, exploiting their excellent Storage capacity and cost per MB characteristics. They also rely upon disk arrays, exploiting their high bandwidth, to satisfy a very large number of requests. Given typical access patterns and server configurations, the tape drives are fully utilized uploading data for requests that “fall through” to the tertiary level. Such upload operations consume significant Secondary Storage Device and bus bandwidth. In addition, with present technology (and trends) the disk array can serve fewer requests to continuous objects than it can store, mainly due to IO and/or backplane bus bandwidth limitations. In this work we address comprehensively the performance of these hierarchical, continuous-media, Storage servers by looking at all three main system resources: the tape drive bandwidth, the Secondary-Storage bandwidth, and the host's RAM. We provide techniques which, while fully utilizing the tape drive bandwidth (an expensive resource) they introduce bandwidth savings, which allow the Secondary Storage Devices to serve more requests and do so without increasing demands for the host's RAM space. Specifically, we consider the issue of elevating continuous data from its permanent place in tertiary for display purposes. We develop algorithms for sharing the responsibility for the playback between the Secondary and tertiary Devices and for placing the blocks of continuous objects on tapes, and show how they achieve the above goals. We study these issues for different commercial tape library products with different bandwidth and tape capacity and in environments with and without the multiplexing of tape libraries.

Peter Triantafillou - One of the best experts on this subject based on the ideXlab platform.

  • Continuous Data Block Placement in and Elevation from Tertiary Storage in Hierarchical Storage Servers
    Cluster Computing, 2001
    Co-Authors: Peter Triantafillou, Thomas Papadakis
    Abstract:

    Given the cost of memories and the very large Storage and bandwidth requirements of large-scale multimedia databases, hierarchical Storage servers (which consist of disk-based Secondary Storage and tape-library-based tertiary Storage) are becoming increasingly popular. Such server applications rely upon tape libraries to store all media, exploiting their excellent Storage capacity and cost per MB characteristics. They also rely upon disk arrays, exploiting their high bandwidth, to satisfy a very large number of requests. Given typical access patterns and server configurations, the tape drives are fully utilized uploading data for requests that “fall through” to the tertiary level. Such upload operations consume significant Secondary Storage Device and bus bandwidth. In addition, with present technology (and trends) the disk array can serve fewer requests to continuous objects than it can store, mainly due to IO and/or backplane bus bandwidth limitations. In this work we address comprehensively the performance of these hierarchical, continuous-media, Storage servers by looking at all three main system resources: the tape drive bandwidth, the Secondary-Storage bandwidth, and the host's RAM. We provide techniques which, while fully utilizing the tape drive bandwidth (an expensive resource) they introduce bandwidth savings, which allow the Secondary Storage Devices to serve more requests and do so without increasing demands for the host's RAM space. Specifically, we consider the issue of elevating continuous data from its permanent place in tertiary for display purposes. We develop algorithms for sharing the responsibility for the playback between the Secondary and tertiary Devices and for placing the blocks of continuous objects on tapes, and show how they achieve the above goals. We study these issues for different commercial tape library products with different bandwidth and tape capacity and in environments with and without the multiplexing of tape libraries.

Ohhoon Kwon - One of the best experts on this subject based on the ideXlab platform.

  • swap aware garbage collection for nand flash memory based embedded systems
    Computer and Information Technology, 2007
    Co-Authors: Ohhoon Kwon
    Abstract:

    Embedded systems use NAND flash memory as a Secondary Storage Device because it has many attractive features such as small size, fast access speeds, shock resistance, and light weight. NAND flash memory based embedded systems exploit a "demand paging" to run applications and also use a "swapping" to extend a limited main memory space. Because the embedded systems use NAND flash memory as swap space, it should perform garbage collection, which is a time-consuming operation. Besides, the number of the erase operations allowed to each block is also limited. In this paper, we propose a new garbage collection policy for embedded systems with the swap system. The proposed garbage collection policy focuses on minimizing the garbage collection time and even wear-leveling. Trace-driven simulations show that the proposed policy performs better than existing garbage collection policies in terms of the garbage collection time and the endurance of flash memory.

Jl Xue - One of the best experts on this subject based on the ideXlab platform.

  • Fine grained, direct access file system support for Storage class memory
    North-Holland, 2017
    Co-Authors: Wang Y, Tz Wang, Liu D, Zl Shao, Jl Xue
    Abstract:

    New Storage class memory (SCM) technologies, such as phase change memory (PCM) and memristors, are not only byte-addressable like DRAM but also non-volatile like traditional hard disk drives. SCM modules can be placed side-by-side with DRAM on the memory bus, available to memory instructions issued by the CPU. This shift thus engenders a new "DRAM-SCM" Storage architecture, which promises near-DRAM Secondary Storage access speed at several orders of magnitude faster than magnetic disk or flash memory. Utilizing SCM as a Secondary Storage Device will have a profound impact on memory hierarchy design, requiring new architectural and operating system support.In this paper, we adopt PCM in the DRAM-SCM Storage architecture and present BSS to provide file system-independent Block Device Support for Storage class memory. To ensure backward compatibility and high performance, BSS provides a block Device interface found in traditional hard disk drives and allows existing file systems to be built on top of itself without any modifications. BSS is designed to directly access the PCM through memory instructions and bypass traditional disk caches that are intended to reduce seek time.The DRAM-SCM architecture and BSS are prototyped in QEMU and the Linux kernel, respectively. Validation using benchmarks reveals that both work together well to exploit significant advantages of SCM. Compared to traditional hard disk drives, our approach boosts the write/read performance by up to 204x for large files and achieves comparable performance for small ones.Department of Computin

Wang Y - One of the best experts on this subject based on the ideXlab platform.

  • Fine grained, direct access file system support for Storage class memory
    North-Holland, 2017
    Co-Authors: Wang Y, Tz Wang, Liu D, Zl Shao, Jl Xue
    Abstract:

    New Storage class memory (SCM) technologies, such as phase change memory (PCM) and memristors, are not only byte-addressable like DRAM but also non-volatile like traditional hard disk drives. SCM modules can be placed side-by-side with DRAM on the memory bus, available to memory instructions issued by the CPU. This shift thus engenders a new "DRAM-SCM" Storage architecture, which promises near-DRAM Secondary Storage access speed at several orders of magnitude faster than magnetic disk or flash memory. Utilizing SCM as a Secondary Storage Device will have a profound impact on memory hierarchy design, requiring new architectural and operating system support.In this paper, we adopt PCM in the DRAM-SCM Storage architecture and present BSS to provide file system-independent Block Device Support for Storage class memory. To ensure backward compatibility and high performance, BSS provides a block Device interface found in traditional hard disk drives and allows existing file systems to be built on top of itself without any modifications. BSS is designed to directly access the PCM through memory instructions and bypass traditional disk caches that are intended to reduce seek time.The DRAM-SCM architecture and BSS are prototyped in QEMU and the Linux kernel, respectively. Validation using benchmarks reveals that both work together well to exploit significant advantages of SCM. Compared to traditional hard disk drives, our approach boosts the write/read performance by up to 204x for large files and achieves comparable performance for small ones.Department of Computin