Memory Primary (RAM) and Secondary (Storage SSD/HDD)

Question 1

What does RAID stand for?

Answer 1

Redundant Array of Independent Disks (Drives). Protects data in drives in case of a drive failure - provides redundancy (except RAID 0)

Question 2

Which level of RAID provides no data redundancy?

Answer 2

RAID 0 is the only RAID level that provides no redundancy as it stripes data across two drives (for faster read/write) if one drive fails all data is lost.

Question 3

What does RAID 5 use to provide redundancy?

Answer 3

RAID 5 uses striping and a parity block to provide redundancy. If a single drive fails the data can be re-built in real time by using the parity data.

The parity block is a separate drive but also the parity information is spread over the other drives.

Question 4

How many disks does RAID 5 require as a minimum?

Answer 4

RAID 5 requires 3+ disk drives (one for the parity block and two+ others to stripe data across).

Question 5

What’s a disadvantage that a RAID 5 setup has but RAID 0 doesn’t have?

Answer 5

Cost as requires 3 drives whereas 0 requires 2.
Speed of reading/writing as the parity calculation may reduce performance.

Question 6

How many disks does RAID 10 (1+0) require as a minimum?

Answer 6

4 drives as data is striped (split) across mirrors (duplicate/mirrored drives).

Data split then split again = 4 blocks of data, hence 4 drives required.

Question 7

What are the 5 types/levels of RAID?

Answer 7

0 - no redundancy but fast 2+ drives striping
1 - one to one copying 2+ drives, can only use 50% storage
5 - data parity block (drive) and striping 3+ drives, one drive space lost due to storing the parity
10 - 1+0, striping across copies/mirrored drives, fast, can only use 50% storage

RAID 6 = RAID 5 but with TWO parity blocks/drives instead of one. Double parity 6.