RAIDS

Question 1

RAIDS (Redundant Array of Inexpensive Disks)

Answer 1

How to make a large, fast, reliable storage system?
Redundant Arrays of Inexpensive Disks
- technique to use multiple disks in concert to build a faster, bigger, more reliable disk system

Question 2

External and Internal View of RAID

Answer 2

Externally, RAID looks a like a disk, or a group of blocks one can read or write
Internally, RAID consists of multiple disk, memory (both volatile and non)
- a hardware RAID is much like a computer system, specialized for the task of managing a group of disks

Question 3

Advantages of RAID over a single disk

Answer 3

• performance, using multiple disks in parallel can greatly speed up I/O times
• capacity
• improve reliability, spreading data without RAID techniques across multiple disks makes the data vulnerable to the loss of a single disk
• with some form of redundancy, RAIDs can tolerate the loss of a disk and keep operating as if nothing were wrong

Question 4

Raid Level 0: Striping

Answer 4

• no redundancy
• striping serves as an upperbound on performance and capacity
• simplest form: stripe blocks across the disks of the system (round robin fashion)
• extract the most parallelism from the array when requests are made for contiguous chunks of the array

Question 5

Transparency enables deployment

Answer 5

transparently, in a way that demands no change to the rest of the system
RAID provides advantages transparently to systems that use them (RAID just looks like a big disk to the host system)

Question 6

stripe

Answer 6

• blocks in the same row (0, 1, 2, 3)