The following figure illustrates status changes to Thin Image cloned pairs.
The following workflow describes Thin Image pair status changes:
- You choose two volumes that are in the SMPL status and are not in use as a Thin Image pair.
- You create a pair. If the P-VOL has not previously been paired with any S-VOL, the pair status changes to COPY at first, and then to PAIR after the pair creation finishes.
- You split a pair. When you split a pair in the PAIR status, the pair status changes to PSUS(SP) or PSUP, and copying data is started asynchronously. When the copy operation completes, the pair status changes to SMPL(PD) or SMPP. When the pair deletion completes, the pair status changes to SMPL. The S-VOL becomes unpaired (a DP-VOL) and can be used as a volume in the same status as the P-VOL. Note: If you delete a pair when the pair status is PSUS(SP) or PSUP, copying data stops at the time when the pair deletion is accepted, and the status changes to SMPL. If this happens, data in the S-VOL is not guaranteed.
- The DP pool can only contain data of predetermined capacity. If the total capacity of data in the pool exceeds the pool capacity, the status of the Thin Image pair changes to PSUE. In addition, the pair status also changes to PSUE if a failure occurs during the process or if the pool usage rate reaches 100 percent. When snapshot data is stored in the DP pool, the timing of changing to PSUE is determined by the setting in "Suspend TI pairs when the deletion threshold is exceeded" in HDvM - SN, or by the setting specified by using the raidcom modify pool -suspend_tipair <yes|no> command in CCI. For details, see the Provisioning Guide for your storage system.
- You delete a pair. When a pair is deleted, the pair status changes to SMPL(PD) or SMPP. After that, it changes to SMPL when pair deletion completes.
Whether the host can read or write data from and to a Thin Image pair P-VOL or S-VOL is determined by the pair status. The following table describes whether the host can access volumes, and their cloned pair status.
| Pair status | Primary volume | Secondary volume | ||
|---|---|---|---|---|
| Read | Write | Read | Write | |
| SMPL | Y | Y | Y | Y |
| COPY | Y | Y | N | N |
| PAIR | Y | Y | N | N |
| PSUS(SP) or PSUP | Y | Y | Y | Y |
| SMPL(PD) or SMPP | Y | Y | Y | Y |
| PSUE | Y | Y | N | N |