RAID question

We just added 2 drives to an S20 that previously had 4 drives on it (one
RAID set).  I used SST to add the new drives to device parity protection
and then added them to my ASP.  As we were not adding a full RAID set, I
expected the system to mirror the devices.  Instead, I see this on the
WRKDSKSTS display:

                    --Protection--            --Protected--
Unit      ASP       Type      Status          Size
1         1    DPY       ACTIVE          3145
2         1    DPY       ACTIVE          3145
3         1    DPY       ACTIVE          3145
4         1    DPY       ACTIVE          3145
5         1    DPY       ACTIVE          4194
6         1    DPY       ACTIVE          4194

This gives more DASD than if the new drives were irrored, but are they
really protected?  If so, why am I seeing all 4194 MB?
We are at V4R1.


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