HP StorageWorks 3000 RAID Array - Manual (Page 53)

RAID Array 3000 Controller 2-11
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 1
RAID 1 (also known as mirroring or shadowing) takes data sent by the host
and duplicates it on all the drives in an array. The result is a high degree of
data availability, since you can lose all but one drive in the array and still have
full access to your data. This comes at a price: a RAID 1 array requires
multiple drives to achieve the storage capacity of a single drive. Figure 2– 6
shows a RAID 1 write.
0010
1011
0110
Host Data
Controller writes
data from cache
to all drives in
the array
SHR-1055
Figure 2-6. Diagram of a RAID 1 write
A RAID 1 array will show up on the monitor as degraded when at least one
drive fails, even if two or more members of the redundancy group remain in
good working order. As long as at least two working drives remain in the
array, you may continue to run the array in degraded mode without putting
data in jeopardy.