Compaq HSZ80 manual Considerations for Planning a RAIDset, 16Creating Storagesets

3–16Creating Storagesets

For example, in a three-member RAIDset that contains disk drives 10000, 20000, and 30000, the first chunk of an I/O request is written to 10000, the second to 20000, then parity is calculated and written to 30000; the third chunk is written to 30000, the fourth to 10000, and so on until all of the data is saved.

The relationship between the chunk size and the average request size determines if striping maximizes the request rate or the data-transfer rate. You can set the chunk size or let the controller set it automatically. See “Chunk Size,” page 3–51,for information about setting the chunk size.

I/O Request

Chunk 1

2 3 4

Disk

10000

Disk

2

0000

Disk

3

0
0
	00

Chunk 1	4	2	Parity	Parity	3
			for	for
			3 & 4	1 & 2

CXO5509A

Figure 3–7. Parity Ensures Availability; Striping Provides Good Read Performance

Considerations for Planning a RAIDset

Keep these points in mind as you plan your RAIDsets:

■A controller can support up to 20 storagesets, consisting of RAIDsets (see Table 3–1).