Hp StorageWorks 1510i Modular Smart Array Manuale Utente Scaricare il pdf (Pagina 145)

A Storage overview

• Arrays and logical drives

• Fault-tolerance levels

• Comparison of RAID Methods

•ChoosingaRAIDlevel

Arrays and logical drives

The capacity and performance of a single physical hard drive is adequate for home users. However,

business users demand higher storage capacities, higher data transfer rates, and greater protection

against data loss when a hard drive fails.

Connecting extra physical drives to a system increases the total storage capacity (Figure 1), but has no

effect on the efﬁciency of read/write operations. Data is still transferred to only one physical drive

at a time.

D1 D2 D3

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Figure1Multiplephysicaldrives(D1,D2,andD3)inasystem

An array c

ontroller combines several physical drives into one or more virtual units called logical drives,

which ha

ve superior performance, capacity, and/or fault tolerant features than separate physical drives.

The read/write heads of all included physical drives are active simultaneously, reducing the total time

required for data transfer.

R/W

D1 D2 D3

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Figur

e 2 Multiple physical drives (D1, D2, and D3) conﬁgured into one logical drive (L1)

Becau

se the read/write heads are active simultaneously, the same amount of data is written to each drive

during any given time interval. Each unit of data is called a block, and adjacent blocks form a set of

data stripes across all physical drives in that logical drive (Figure 3).

1510i Modular Smart Array Command Line Interface user guide

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Hp StorageWorks 1510i Modular Smart Array Manuale Utente Pagina 145