File management

1

• File management

2

• File Systems Architecture

• File organization and access
• sequential
• index-sequential
• direct

3

• File sharing and blocking

• 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

4

• File allocation

• 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

5
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