Ch. 12: Mass-Storage Systems

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What is storage area network?

A private network connecting servers and storage units

In Host-Attached storage, disks can be attached to the computers directly via an ___

I/O Bus

_____ is rate at which data flow between drive and computer.

Transfer rate

____ is much more expensive than disk storage

main memory

What is seek time?

move disk to the target cylinder

Circular-SCAN is designed to ____

provide a more uniform wait time

positioning time is also called ___

random-access time

_____ is difficult for OS to calculate

rotational latency

Disk scheduling usually tries to minimize ____

seek time

Positioning time includes ____ and _____

seek time rotational latency

Tape is best for _____, ___ is much slower

sequential access random access

What does SSTF stand for?

shortest seek time first

Network-Attached Storage is ____

storage made available over a network instead of a local bus

What is rotational latency?

for the target sector to rotate under the disk head

Fiber Channel is ______

high-speed serial bus

Disks can be attached to the computer as:

host-attached storage network-attached storage storage area network

What is swap space?

disk space used by virtual memory as an extension of the main memory

What is Physical formatting

divide disk into sectors for controller to read/write

SCAN algorithm sometimes is called the ___

elevator algorithm

A _____ is likely to be more reliable than a ________

fixed disk removable disk or tape

Disk scheduling performance depends on the _____

# and types of requests

Which is the simplest scheduling algorithm?

FCFS

There are many disk scheduling algorithms: (5)

FCFS SSTF SCAN C-SCAN C-LOOK

______ provide bulk of secondary storage of computer system

Magnetic disks

____ is responsible for using hardware efficiently

OS

_____ is time to move disk arm to desired sector

Positioning time

___ and ____ moves head end to end, even no I/O in between

SCAN and C-SCAN

RAID can only detect/recover from ___

disk failures

What is Access latency?

amount of time needed to locate data

What is the average access time of a magnetic disk?

average seek time + average latency

Bandwidth is measured in ____

bytes per second

What is disk bandwidth?

the speed of data transfer, data/time data: total number of bytes transferred time: between the first request and completion of the last transfer

What are tertiary storage devices?

third level (after memory and magnetic disks) e.g. floppy disks, CD-ROMs, DVDs, usually removable, low cost

Disk Scheduling chooses ____

which pending disk request to service next


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