Week 5 - Data Storage Flashcards
Do hard disks normally store data magnetically or electronically?
Magnetically.
How is information stored on hard disks? Hint: Not magnetically or Electronically.
Information on a hard disk is stored on platters. The information on these platters is accessed by a read-write head.
What is an Actuator in terms of hard disks?
An Actuator is what moves the read-write head to different locations on the platter.
What is an Platter in terms of hard disks?
What the data is stored on.
Platters can be double sides to store more data.
TRUE OR FALSE: You can only have one platter in a hard disk.
FALSE. You can have more than one.
What is the Read-Write head in terms of hard disks?
The pointer that points to the location of the data to be accessed. It is physical and hovers above the platter at that location.
What are the three parts to a platter structure? These are what platters are organised into.
Track
Sector
Cluster
Geometric Sector
What is a Track in a Platter?
A circular section that goes around the platter.
What shape is a Platter?
A circle, with a hole in the middle.
What is a Sector in a Platter?
A segment of a track.
What is a Cluster in a Platter?
A sequence of adjoining sectors on the same track. They join on their short sides.
What is a geometric sector in a Platter?
A number of sectors on different tracks, joining vertically reaching from the certain of the platter out to the each. Looks like a slice of pie (Platter is a circle).
How much data does a sector normally contain?
Just over 512 bytes.
512 of it for the storage, and some more data to store header data etc..
What is stored in a sector?
The actual data
Header
Synchronisation Area
Cyclic Reducancy Checker value (CRC)
What is the Synchronisation area?
An area used internally by the disk to guide the read process in that sector.
What is the Header area?
An area that stores data on the sector number, location and status info.
What is the Cyclic Redundacy Checker Value (CRC)?
Data used to ensure the integrity of the data in the sector.
What secotrs are the most used/visited?
The outer rings of sectors.
Why are Clusters used as storage sets?
Because sectors themselves are often too small to store all the data in a file. Thus, sectors are grouped into clusters.
What is a Cylinder in terms of hard disks?
Multiple platters stacked on top of each other.
What is Logical Block Addressing (LBA)?
A way of numbering sectors in multiple platters. IT uses a linear index scheme: first block is LBA 0, the second is LBA 1 etc..
LBA acts as a physical address to these locations on the platters.
How many bits are used for addressing in LBA?
48 bits.
Where is the Master Boot Record stored?
In the first sector of the main hard disk: LBA 0.
What does the Mater Boot Record do?
It allows for the system to actually boot and startup. IT also stores data on partition tables for disks.
