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Understanding File Management and Access Methods: LIOCS, PIOCS, and Storage Solutions

This article delves into file management access methods, including Logical I/O (LIOCS) and Physical I/O (PIOCS), along with the role of device drivers in file systems architecture. Explore file organization techniques such as sequential, index-sequential, and direct access. Understand file sharing, access rights, locking mechanisms, and the importance of record blocking. The discussion extends to file allocation methods, RAID configurations for data redundancy, and the differences between Storage Area Networks (SAN) and Network Attached Storage (NAS). Enhance your knowledge on optimizing storage efficiency and performance strategies.

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Understanding File Management and Access Methods: LIOCS, PIOCS, and Storage Solutions

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Presentation Transcript

  1. File management

  2. access methods logical I/O (LIOCS) physical I/O (PIOCS) device drivers File Systems Architecture File organization and access • sequential • index-sequential • direct

  3. block data block data block data IBG IBG IRG IRG IBG • File sharing • access rights: read, write, execute, by user classes. • File/record locking: simultaneous access • Record blocking • Logical vs physical record • unblocked vs blocked record • fixed-length vs variable-length File sharing and blocking

  4. File allocation table (FAT) • Pre allocation vs dynamic allocation • Portion size • contiguity increases performance • fixed-size portions simplify reallocation • variable-size or small fixed-size minimizes waste of unused space for overallocation • two main alternatives: • variable, large contiguous portions (performance) • small fixed portions (flexibility) • File fragmentation and reorganization File allocation

  5. strip 0 strip 1 strip 2 strip 3 strip 4 strip 5 strip 6 strip 7 strip 9 strip 10 strip 11 strip 8 strip 13 strip 15 strip 14 strip 12 Redundant Array of Independent/ Inexpensive Disks (RAID) • RAID is a set of physical disk drives viewed by the OS as a single logical drive • Data are distributed across the physical drives of an array • Redundant disk capacity is used to store parity information, which guarantees data recovery • RAID Levels: various levels of performance and redundancy • the disks are divided in strips: physical blocks, sectors, or similar • the strips are mapped round robin on the array • I/O requests can be processed in parallel

  6. Storage Management • Storage Area Network (SAN) • Building a Storage Area Network • Fiber and IP • Network Attached Storage (NAS) • SAN and NAS topology • NAS and interoperability • Comparison of SAN and NAS • SAN and NAS comparison

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