The following is provided to help you prepare TrueCopy volumes:
- A volume can be assigned to only one pair.
- Logical units on the primary and secondary storage systems must be defined and formatted prior to pairing.
- The P-VOL and S-VOL must have the same capacity.
- TrueCopy requires a one-to-one relationship between the P-VOL and S-VOL. The P-VOL cannot be copied to more than one S-VOL, and an S-VOL cannot have more than one P-VOL.
- Logical Unit (LU) types
- TrueCopy supports OPEN-V.
- Pair volumes must consist of LUs of the same type and capacity.
- The LUN paths must be defined for both P-VOL and S-VOL, or both P-VOL and S-VOL must be defined as namespaces on the NVM subsystems to which NVM subsystem ports have been added.
- TrueCopy operates on volumes rather than on files. Multi-volume files require special attention. For complete duplication and recovery of a multi-volume file (for example, a large database file that spans several volumes), make sure that all volumes of the file are copied to TrueCopy S-VOLs.
- TrueCopy pair volumes can be shared with non-TrueCopy Hitachi software products. For details, see Sharing TrueCopy volumes.
- TrueCopy uses Virtual LUN (VLL) when creating external volumes in an external volume group. When custom-size LUs are assigned to a TrueCopy pair, the S-VOL must have the same capacity as the P-VOL. You can use CCICCI to check the LUs of the P-VOL and S-VOL.
- Because the contents of the P-VOL and S-VOL are identical, the S-VOL can be considered a duplicate of the P-VOL. Because the host operating system does not allow duplicate volumes, the host system administrator must take precautions to prevent system problems related to duplicate volumes. You must define the S-VOLs so they do not auto mount or come online to the same host at the same time as the P-VOLs.
TrueCopy does not allow the S-VOL to be online (except when the pair is split). If the S-VOL is online, the TrueCopy paircreate operation will fail.
CAUTION:When P-VOLs and S-VOLs are connected to the same hosts, define the S-VOLs to remain offline even after the hosts are restarted. If a pair is released and a host is subsequently restarted, the S-VOL should remain offline to prevent errors due to duplicate volumes.