Database System: Storage

Question 1

Block

Answer 1

A logical unit consisting of a fixed number of contiguous sectors.

Block size is fixed during initialisation and cannot be changed dynamically. The block size ranges from 512B to 8Kb

Question 2

Input/Output I/O

Answer 2

The transfer of one block between main memory and hard disk

The number of I/O is used to evaluate the efficiency of a data structure/algorithm.

A block can be called a page in database

Question 3

Database in file storage

Answer 3

A collection of filles on disk

Question 4

File

Answer 4

A collection of blocks

Question 5

A block

Answer 5

Can contain tones metadata, indexes, log records

Question 6

Pin

Answer 6

Number of threads accessing the page

Question 7

Hit rate

Answer 7

The total number of hits over the total number of requests

Question 8

Buffer replacement policy

Answer 8

When the DBMS needs to free up a frame to make room for a new page, it must decide which page to evict from the buffer pool.

LRU
Clock
MRU

Question 9

RAID

Answer 9

Redundant Array of Independent Disks

It’s a method of storing the same data on multiple hard disks. By placing data in multiple disks, I/O operations can overlap in a balanced way, improving performance. Because multiple disks increase the mean time between failures (MTBF) and storing data independently increases fault tolerance.

Question 10

Buffer pool

Answer 10

Available main memory used for storing copies of disk blocks

Question 11

Buffer manager

Answer 11

A DBMS subsystem that manages the buffer pool, aiming at minimizing I/Os.

Component of the DBMS that manages the memory and the move of data between the main memory and the disk