An input/output (I/O) device can incorporate mechanical devices that require physical movements, such as a hard drive seeking a track for a data read or write. Hence I/O operations on a computer can be extremely slow compared to data processing. When a program conducts many I/O operations, the processor often spends most idling as it waits for the I/O operations to complete. The same holds true for a virtual machine (VM), and to improve the overall performance of a VM, this problem needs to be addressed. In this paper, we propose a pinning technique, which migrates frequently accessed disk blocks from hard disks to flash memories, to reduce the I/O waiting time. Experimental results show that the start-up times dramatically decrease by up to 38% on average when using this method.
Hard disks are one of the largest sources of power consumption in large-scale storage systems. The disk spin up/down technique has been shown to be an effective solution to this problem. Accordingly, the Open Compute Project (OCP) proposed a storage server for cold data, known as Cold Storage, to reduce power consumption using the spin-down technique in large-scale storage systems. With the aim of making effective use of Cold Storage, we characterize the power consumed by a hard disk in its various modes of operation. We then analyze the workload of an instant messaging service. These our contributions should provide guidelines for the implementation of a stable and energy-efficient distributed file system on a Cold Storage server, and to establish a spin-down policy that is power-proportional and promotes reliability.
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