• Journal of KIISE:Computing Practices and Letters
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• v.14 no.6
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• pp.594-598
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• 2008

In this paper we propose a fast booting technique based on Improved snapshot boot in embedded Linux, widely adopted in personal devices such as PDA and mobile phones. The existing Snapshot boot technique tries to create a snapshot image at the time of suspend, and later load the entire snapshot image into the system memory at the predefined location with the help of a bootloader at the time of resume. Since a bootloader has to copy the entire snapshot image into the predefined memory to resume the previous suspended computing state, a little bit long time is required to resume. Improved snapshot boot does not create a snapshot image consisting of whole memory pages at the time of suspend, thus resulting in smaller snapshot image than the existing snapshot boot. The remaining pages are in the swap area. The resulting smaller sized snapshot image enables much faster booting latency. Through the experiment, we can see the booting latency is reduced almost 30% with suspend image of 2982 pages. This result depends on the amount of swap-out pages.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.4
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• pp.88-95
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• 2010

As the development of IT technologies, storages stored very sensitive data which should not be damaged, too. It increased the importance of data backup and makes the time need to backup data important issues. Snapshot is one of the backup technologies which needs short downtime to maintain consistency of data during backup data. In this paper, we studied two kinds of snapshots, local file system based snapshot and network file system based snapshot. In the local file system based snapshot part, we propose the PSnap which is a snapshot library for non-snapshot file system as like Ext2, Ext3 and XFS. In another part, network file system based snapshot, we propose the GlorySnap which snapshot utilities for GloryFS is a distributed file system was made by ETRI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3B
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• pp.254-259
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• 2011

This paper attempts to propose a method to improve the snapshot boot method, one of the methods to enhance the booting speed of the embedded Linux based system and to increase its efficiency. Snapshot boot is a method of using suspend/resume that is a method of saving and restoring the entire information of the current tasks, and it enhances the booting speed by processing a restoration of previous tasks from the bootloader instead of processing the Linux booting. The facing problem of snapshot boot is that it takes a long time to create images and save them to the storage device during the suspend process since it targets every pages. Additionally, if the switch is turned off while creating an image by some extraordinary circumstances, then the image is not created and thus, the resume process of snapshot boot cannot be executed. The suggest method in this paper creates the snapshot image for once only and utilize the image to enhance the speed and stability on booting.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.108-121
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• 2004

In this paper, we propose an enhanced snapshot technique that solves performance degradation when snapshot is initiated for the storage cluster system. However, traditional snapshot technique has some limits adapted to large amount storage shared by multi-hosts in the following aspects. As volume size grows, (1) it deteriorates crucially the performance of write operations due to additional disk access to verify COW is performed. (2) Also it increases excessively the blocking time of write operation performed during the snapshot creation time. (3)Finally, it deteriorates the performance of write operations due to additional disk I/O for mapping block caused by the verification of COW. In this paper, we propose an efficient snapshot technique for large amount storage shared by multi-hosts in SAN Environments. We eliminate the blocking time of write operation caused by freezing while a snapshot creation is performing. Also to improve the performance of write operation when snapshot is taken, we introduce First Allocation Bit(FAB) and Snapshot Status Bit(SSB). It improves performance of write operation by reducing an additional disk access to volume disk for getting snapshot mapping block. We design and implement an efficient snapshot technique, while the snapshot deletion time, improve performance by deallocation of COW data block using SSB of original mapping entry without snapshot mapping entry obtained mapping block read from the shared disk.

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.417-425
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• 2019

Storage snapshot technology allows to preserve data at a specific point in time, and recover and access data at a desired point in time. It is an essential technology for storage protection application. Existing snapshot methods have some problems in that they dependent on storage hardware vendor, file system or virtual block device. In this paper, we propose a new snapshot method for solving the problems and creating snapshots on-line. The proposed snapshot method uses a method of extracting the log records of update operations at the virtual file system layer to enable the snapshot method to operate independently on file systems, virtual block devices, and storage hardwares. In addition, the proposed snapshot mehod creates and manages snapshots for directories and files without interruption to the storage service. Finally, through experiments we measure the snapshot creation time and the performance degradation caused by the snapshot.

• Journal of KIISE
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• v.44 no.9
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• pp.871-877
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• 2017

A vast amount of research has been carried out for executing compute-intensive applications on resource-constrained mobile devices. Computation offloading is a method in which heavy computations are dynamically migrated from a mobile device to a server, exploiting the powerful hardware of the server to perform complex computations. An important issue for offloading is the complexity of reconciling the execution state of applications between the server and the client. To address this issue, snapshot-based offloading has recently been proposed, which utilizes the snapshot of a web app as the portable description of the execution state. However, for web applications using the HTML5 canvas, snapshot-based offloading does not function correctly, because the snapshot cannot capture the state of the canvas. In this paper, we propose a code generation technique to save the canvas state as part of a snapshot, so that the snapshot-based offloading can be applied to web applications using the canvas.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.55-58
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• 2005

In multi-level storage system with snapshot data, some snapshots which are from selection portions of the base tables are kept in main memory. So how to efficiently refresh snapshots in response to changes on their base tables for preserving consistency which requires snapshots reflect the current state of the base tables referenced by the snapshot query is a very import research issue. In this paper, a method for efficiently refreshing snapshots is proposed. In this method, it uses a data structure to store metadata which contains some necessary information of every snapshot and an updating log that records the history of changes on its base tables. Synchronization process scans the metadata and refreshing process is executed using appropriate logs after it finds anyone of the snapshot need to be refreshed.

• Bulletin of the Korean Mathematical Society
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• v.41 no.2
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• pp.327-335
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• 2004

In this paper, we reformulate a snapshot attractor([5]), ($K,\;\={\mu_{\iota}}$) generated by a random baker's map with a sequence of probability measures {\={\mu_{\iota}}} on K. We obtain bounds of the correlation dimensions of ($K,\;\={\mu_{\iota}}$) for all ${\iota}\;{\geq}\;1$.

• Current Optics and Photonics
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• v.4 no.4
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• pp.345-352
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• 2020

We describe a calibration method to improve the accuracy of interferometric snapshot spectroscopic ellipsometry employing a dual-spectrometer sensor scheme. Conventional spectral wavelength calibration of a spectrometer has been performed by using a calibration lamp having multiple peaks at specific wavelength. This paper shows that such a conventional spectrometer calibration method is inappropriate for the proposed interferometric snapshot spectroscopic ellipsometry to obtain highly accurate ellipsometric phase information. And also, systematic error analysis of interferometric snapshot spectroscopic ellipsometry is conducted experimentally.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10a
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• pp.257-258
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• 2007