HP StorageWorks 3000 RAID Array - Manual (Page 56)

2-14 RAID Array 3000 Controller Shelf Hardware User’s Guide
Compaq Confidential – Need to Know Required
Writer: Bob Young Project: RAID Array 3000 Controller Shelf Hardware User’s Guide Comments:
Part Number: EK-SMCPQ-UG. D01 File Name: c-ch2 RAID Array 3000 Controller.doc Last Saved On: 12/4/00 1:08 PM
RAID 4
RAID 4 breaks up host data into chunks, calculates parity by performing an
exclusive-or on the chunks, and then writes the chunks to all but one drive in
the array and the parity data to the last drive (Figure 2– 8). When the host
requests data from the disk drives, the controller retrieves the chunks
containing the addressed data, reconstitutes the data from the chunks, and
passes the data to the host.
0011
1011
0110
1110
0110
0000
1111
1110
Host Data
Controller divides the
data into chunksized units
and calculates parity
There is still data left
so the Controller
repeats the Process
0011
0011
0110
0110
1011
1011
0000
0000
0110
0110
1111
1111
1110
1110
1110
1110
Striped data and parity
written to the array
Striped data and parity
written to the array
SHR-1057
0000
0111
XOr
XOr
Parity =
Parity =
Figure 2-8. Diagram of a RAID 4 write