Hp Smart Array 6i Controller and 128MB BBWC Manuale Utente Scaricare il pdf (Pagina 47)

Drive Arrays and Fault-Tolerance Methods 47

HP CONFIDENTIAL

File Name: 347914-1.doc Last Saved On: 1/26/04 9:31 AM

Write performance High Medium Low Low

This method is most useful when data loss is unacceptable but cost is also an

important factor. The probability that data loss will occur when an array is

configured with RAID ADG is less than it would be if it were configured with

RAID 5.

Advantages:

• Has a high read performance.

• Allows high data availability—any two drives can fail without loss of critical

data.

• More drive capacity is usable than with RAID 1+0—parity information

requires only the storage space equivalent to two physical drives.

Disadvantages:

The main disadvantage of RAID ADG is a relatively low write-performance

(lower than RAID 5), because of the need for two sets of parity data.

Comparing the Hardware-Based RAID Methods

NOTE: Not all controllers support RAID ADG.

Item RAID 0 RAID 1+0 RAID 5 RAID ADG

Alternative name Striping

(no fault

tolerance)

Mirroring Distributed

Data

Guarding

Advanced

Data

Guarding

Usable drive space* 100% 50% 67% to 93% 50% to 96%

Usable drive space formula n n/2 (n-1)/n (n-2)/n

Minimum number of physical drives 1 2 3 4

Tolerates failure of one physical

drive?

No Yes Yes Yes

Tolerates simultaneous failure of

more than one physical drive?

No Only if no two

failed drives are

in the same

mirrored pair

No Yes

Read performance High High High High

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 55 56

Commenti su questo manuale

Nessun commento

Hp Smart Array 6i Controller and 128MB BBWC Manuale Utente Pagina 47

Commenti su questo manuale

Prodotti e manuali riguardandi Accessori per computer Hp Smart Array 6i Controller and 128MB BBWC