Understanding Raid Level-1 - IBM Netfinity ServeRAID-3H Installation And User Manual

Though the risk of data loss is present, you might want to assign RAID level-0 to one of the logical drives
to take advantage of the speed offered with this RAID level. You could use this logical drive to enter data
that you back up each day and for which safety is not of primary importance, that is, data that you can
re-create easily. You also might want to use a RAID level-0 logical drive when the work you are doing
requires maximum capacity.

Understanding RAID Level-1

RAID level-1 provides 100% data redundancy and requires only two physical drives. With RAID level-1,
the first half of a stripe is the original data; the second half of a stripe is a mirror (that is, a copy) of the
data, but written to the other drive in the RAID level-1 array.
Because the data is mirrored, the capacity of the logical drive when assigned RAID level-1 is 50% of the
array capacity.
The following illustration shows an example of a RAID level-1 logical drive.
You start with two physical drives.
Create an array using the two physical drives.
Then, create a logical drive within that array.
The data is striped across the drives, creating blocks.
Notice that the data on the drive on the right is a mirror
copy of the drive on the left.
With RAID level-1, if one of the physical drives fails, the ServeRAID controller switches read and write
requests to the remaining functional drive in the RAID level-1 array.
6
IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers
1 1
2 2
3 3
4 4