Lecture 1 Flashcards
What is the blocking factor?
The number of records per block
What is data transfer time?
The time taken to access a disk address and transfer a block of data
How do you calculate DTT?
T= A + R/2 + L/D
A: Access motion time
R: Rotational delay
L: Length of block
D: Data transfer rate
What is parity?
Extra data used to calculate any missing data or verify stored data’s integrity/
What is disk striping?
the process of dividing a body of data into blocks and spreading the data blocks across multiple storage devices
What is RAID?
Redundant Array of Inexpensive Disks is a way of storing data in different places on multiple hard disks to protect data in the case of a drive failure.
Describe RAID 0
Uses striping
NOT Fault tolerant
Focuses on speed i.e maximizing read/ write access
Describe RAID 1
Disk mirroring
Designed for reliability
Describe RAID 5
Striping with parity
Requires at least 3 disks
Loses space for storing parity (equal to one disk).
Is fault tolerant because of the parity
RAID 10 (1+0)
Mirroring data that is then striped across.
Can only use 50% for storage due to backup
What are the two types of database data?
Log data and table data
What data does RAID 1 store?
Log data
What data does RAID 5 store?
Table data
T/F RAID 1 is cheaper than RAID 5
False
Rebuilding is easiest with RAID level….
RAID 1
