HP StorageWorks XP Business Copy Software user guide: HP XP12000 Disk Array, HP XP10000 Disk Array, HP 200 Storage Virtualization System (T1713-96027, April 2010)
• MU=1 is the number of the same volume for its next pair.
• MU=2 is the number of the same volume for its third pair.
• The MU number of an S-VOL is always MU=0.
For Level 1 (L1) pairs, the root volume could have MU=0, MU=1, and MU=2. For L1 pairs, the
associated S-VOLs all have MU=0 because this is the first pair of which they are a member.
For the Level 2 (L2) pairs, the L1 S-VOLs are now all acting as L2 P-VOLs. Because they are already
a member of one pair, the next MU number for each of them is MU=1 for their first L2 pair and MU=2
for their second L2 pair. For the S-VOLs associated with each of these pairs, the MU number is once
again MU=0 because this is the first pair of which they are a member.
Figure 12 Cascade pairs
.
When L1 and L2 cascade pairs are created, the P-VOLs and S-VOLs of the cascade pairs are classified
using the following terms (as shown in the previous figure):
• The root volume is the P-VOL of the L1 pair, which is the original BC pair. You can add up to three
S-VOLs (node volumes) to a root volume.
• The node volume is the S-VOL (reserved) of an L1 pair and the P-VOL of an L2 pair. You can add
up to two S-VOLs (leaf volumes) to a node volume.
• The leaf volume is the S-VOL (reserved) of an L2 cascade pair.
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