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the pair status changes to COPY(RS-R). When the operation completes, the pair status changes
to PAIR.
6. A pool can contain only a predefined amount of data. If the total capacity of the snapshot
data in the pool exceeds the pool capacity, the pair status changes to PSUE. The pair status
also changes to PSUE when a failure occurs while restoring the pair or when the usage rate
of the pool reaches 100 percent. The pair status may change to PSUE when the failure occurs
during a process other than restoring.
Whether the host can read and write the P-VOL or S-VOL of an XP Snapshot pair depends on the
status of the pair. Table 2 (page 16) shows the relationship between the pair status and the
availability of the host access.
Table 2 Whether Hosts Can Access P-VOL and S-VOL
S-VOLP-VOLPair Status
WriteReadWriteRead
——YesYesSMPL
NoNoYesYesCOPY
NoNoYesYesPAIR/PFUL
YesYesYesYesPSUS/PFUS
NoNoYesYesSMPL(PD)
NoNoYesYesCOPY(RS)
NoNoYesYesCOPY(RS-R)
NoNoYes*Yes*PSUE
Yes: Host can access the volume.
No: Host cannot access the volume.
*: If the pair status changes to PSUE because of a failure during restoration, the host cannot access
that pair.
CAUTION: If the host computer uses application software to monitor the volumes of the XP
Snapshot pairs, problems such as an abnormal end may occur. For example, because the S-VOL
whose status is not PSUS (or PFUS) rejects the access from the host, problems may occur on the
monitoring application software whose access is rejected. In addition, if the host computer connects
to more than one port, problems may also occur on the ports that are not connected to the S-VOL
that rejected the host access. You need to terminate the application software which monitors the
volumes in order to solve these problems.
Use RAID Manager commands to operate XP Snapshot pairs. However, whether or not the
operations complete normally depends on the status of the pairs. Table 3 (page 16) shows the
pair statuses and the results of the RAID Manager commands.
Table 3 Pair Statuses and the Results of the RAID Manager Commands
RAID Manager CommandPair Status
pairsplit -Epairsplit -Spairresync
-restore
pairresyncpairsplitpaircreate
−split
paircreate
NoNOPNoNoNoNoYesSMPL
NoNoNOPNOPNoNoNOPCOPY
NoYesNOPNOPYesYesNOPPAIR / PFUL
16 About XP Snapshot Operations