CH6
what is raid parity
Parity computations are used in RAID drive arrays for fault tolerance by calculating the data in two drives and storing the results on a third. (used in level 6)
which raid level uses complete redundancy?
Raid level 1
-Once the head is in position, the read or write operation is then performed as the sector moves under the head -This is the data transfer portion of the operation
Transfer time
-The sum of the seek time and the rotational delay -The time it takes to get into position to read or write
access time
applications of raid 1
accounting, payroll, financial
disadvantages to raid 1
high disk overhead of all RAID types. Level storage since data is written into 2 locations
disadvantages of raid 0
if there is a drive failure, all date will be lost because its located in one array
what does complete redundancy mean?
is a way of storing the same data in different places on multiple hard disks to protect data in the case of a drive failure.
level 0 compared to level 1
level 0 uses stripping, so its typically faster than Raid 1. Raid 1 also uses stripping, However Level 1 is more secure because it writes all data in 2 locations for protection of drive failure.
A disk in a circular platter constructed of nonmagnetic material, called the substrate, coated with a magnetizable material -Traditionally the substrate has been an aluminium or aluminium alloy material
magnetic disk
why is raid level 1 100% redundant?
there is no rebuild necessary because a backup there is a copy of the disk (since theres 2 locations)
Benefits of the glass substrate magnetic disk:
-Improvement in the uniformity of the magnetic film surface to increase disk reliability -Greater ability to withstand shock and damage
Addresses the issues of request patterns of the host system and layout of the data. Raid 0 or 1
0
which raid level is faster? (0 or 1)
0
Raid level 1: Data striping is used but each logical strip is mapped to ___ separate physical disks so that every disk in the array has a mirror disk that contains the same data
2
raid Consists of ___ levels
7
why is raid 1 completely redundant?
It mirrors its data by having multiple locations in case of drive failure
-modern hard disk systems use a technique known as____ in which the surface is divided into a number of concentric zones -this technique also increases track density
Multiple zoned recording
what is raid mirroring?
RAID 1 writes and reads identical data to pairs of drives. This process is often called data mirroring and it's a primary function is to provide redundancy.
RAID 1 can also be implemented without data striping, although this is less common. T/F
T
-rate by rotating the disk at a fixed speed, known as the
constant angular velocity
which type of disk? -Magnetizable coating is applied to both sides of the platter
double sides disk
advantages to raid 6
extremely high data fault tolerance, and can sustain multiple drive failures. The system will continue to run after 2 disk failures (great for mission critical situations)
which type of disk? -One read-write head per track -Heads are mounted on a fixed ridged arm that extends across all tracks
fixed-head disk
why is raid 6 so secure?
has block level stripping with multiple parity distributed(parity provides fault tolerance)
disadvantages to raid 6
more complex controller design
which type of disk? -One read-write head -Head is mounted on an arm -The arm can be extended or retracted
movable-head disk
which type of disk? -Permanently mounted in the disk drive
non-removable disk -The hard disk in a personal computer is a non-removable disk
RAID 0 (disk stripping) is the process of ...
of dividing a body of data into blocks and spreading the data blocks across multiple storage devices, such as hard disks or solid-state drives (SSDs), in a redundant array of independent disks (RAID) group.
which type of disk? -Can be removed and replaced with another disk
removable disk
-The time it takes for the beginning of the sector to reach the head
rotational delay
-On a movable-head system, the time it takes to position the head at the track
seek time
advantages of raid 0
simple design, easy to implement
applications of raid 0
video game production and editing(can keep up with speed) and image editing