RX-NAS (Replicated eXpandable Network-Attached Storage), a scalable, reliable clustered NAS system designed for entry-level NAS, has been developed. RX-NAS is based on X-NAS, which is a simple clustered NAS architecture for entry-level NAS, and improves the reliability of X-NAS by adding new sets of X-NASs to the original one. The core feature of RX-NAS, namely on-line replication, replicates original file objects to new sets of X-NASs for each file block in real-time without changing clients' environments. RX-NAS has other key features for maintaining the manageability of entry-level NAS; namely, new synchronization and resynchronization functions can easily replicate original files and directories to other X-NAS systems completely or partially without changing clients' environments. In addition, its health-check function can eliminate a limitation on the configuration of RX-NAS and detect and report errors that occur in the RX-NAS system. To validate the RX-NAS concept, an RX-NAS prototype was designed and tested according to the NFSv3 implementation. These tests show that the RX-NAS improves system reliability while maintaining 80% of the throughput of X-NAS.

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It has been noted that the downtime of medical informatics systems is often long. Many systems encounter downtimes of hours or even days, which can have a critical effect on daily operations. Such systems remain especially weak in the areas of database and medical imaging data. The scheme design shows the three-layer architecture of the system: application, database, and storage layers. The application layer uses the DICOM protocol (Digital Imaging and Communication in Medicine) and HTTP (Hyper Text Transport Protocol) with AJAX (Asynchronous JavaScript+XML). The database is designed to decentralize in parallel using cluster technology. Consequently, restoration of the database can be done not only with ease but also with improved retrieval speed. In the storage layer, a network RAID (Redundant Array of Independent Disks) system, it is possible to construct exabyte-scale parallel file systems that exploit storage spread. Development and evaluation of the test-bed has been successful in medical information data backup and recovery in a network environment. This paper presents a schematic design of the new medical informatics system that can be accommodated from a recovery and the dynamic Web application for medical imaging distribution using AJAX.

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