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M3_Review-Chapter10
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M3_Review-Chapter10
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# CSC360
Operating Systems
Midterm #3 review.
Storage Management - Chapter 10
Slide: Mass Storage
Magnetic Disk:
□ provides the bulk of secondary storage for modern computer systems
□ date rate:
□ the rate at which data flows between the drive and the computer.
□ Access Time:
□ consists of two parts:
1) seek time - the time necessary to move the disk arm to the desired cylinder
2) rotational latency - the time necessary for the desired sector to roate to the disk head
□ Interface: ATA, SATA, SCSI, FC, etc
Magnetic Tape:
□ used mainly for backup
Network Attached Storage (NAS)
□ EG. file shares home directories...
Storage Area Network
□ block storage
Disk Scheduling:
□ First come first server:
□ simplest scheduling
□ not the fastest service
□ SSTF Scheduling: (Shortest-seek-time-first)
□ not optimal but better than FCFS
□ reduces head movement
□ starvation is a posibility
□ SCAN scheduling: (elevator algorithm)
□ The head continuously scans back and forth across the disk
□ C-SCAN Scheduling: (circular scan)
□ similar to SCAN scheduling except skips all reqeuest on its return trip to the beginning of disk
□ fairness
□ Look scheduling:
□ looks for closest request and proceeds to it.
Disk Management
□ Physical formatting
□ creating physical sector structures
□ Physical Formatting:
□ before disk can store data, it must be divided into sectors that the disk controller can read and write.
□ Before it can use the disk to hold files, the OS needs to record its own data structures on the disk.
1) Partition disk into one or more groups of cylinders.
2) Logical formatting
□ creation of a file system.
Swap-Space management:
□ Swap space
□ disk space as an extension on main memory
□ Swap-space location:
□ a regular big file
□ swap partition
□ Swap-space management
□ text vs Data segment
□ proactive vs reactive allocation
Raid
□ is a data storage virtualization technology taht combines multiple physical disk drive components into a single
logical unit for the purposes of data redundancy, performance improvement or both.