Expanding the DP-VOL capacity used in a ShadowImage pair

You can expand the capacity of a DP-VOL used as a ShadowImage pair volume.

You can expand the DP-VOL capacity used in an SI pair alone. To expand the DP-VOL capacity in a configuration where an SI pair shares the same volumes with other software, see the User Guide for the remote replication that shares the same volume with the SI pair.

Note: If a DP-VOL capacity is expanded from 4 TB or less to more than 4 TB, all of the allocated area before the expansion is copied when the first pair resync operation (Normal Copy or Reverse Copy) is performed after the expansion, or the first pair split operation is performed after a pair quick resync operation (Quick Resync or Quick Restore).

Therefore, the first pair resync operation (Normal Copy or Reverse Copy) after the expansion, or the first pair split operation after the pair quick resync operation (Quick Resync or Quick Restore) will take a while to complete. The copy progress percentage might be displayed as 100% even before the copy operation is complete.

A V-Vol to be expanded is not an external volume.
The LDEV format is being performed on a V-Vol to be expanded.
A pool containing a V-Vol to be expanded meets any of the following conditions:
- Normal condition
- The used capacity of the pool exceeds the depletion threshold.
- The pool is being shrunk.
A V-Vol to be expanded is a volume created on the storage systems described in Expanding the DP-VOL capacity while keeping the pair status.
A V-Vol to be expanded is not used in a pair with the clone attribute.
The following numbers of tables required after the expansion do not exceed the maximum number allowed on the storage system:
- The number of differential tables
- The number of pair tables

Calculating the numbers of differential and pair tables for each pair

Note: If a DP-VOL exceeds 4 TB, the differential tables are placed in the hierarchy memory instead of the shared memory, and the differential tables in the shared memory are not used. Therefore, it is not necessary to calculate the number of differential tables for DP-VOLs over 4 TB.

The number of differential tables required for each pair.
Calculate how many differential tables are required for each pair using the following formulas:
```
number-of-differential-tables-for-expansion = number-of-differential-tables-after-expansion - number-of-differential-tables-before-expansion
```
```
number-of-differential-tables-per-pair = ceiling ((volume-capacity [KB] / 256) / 20,448)
```
In the example, 'ceiling' refers to rounding up the value enclosed in parenthesis ( ) to the next integer.
The number of pair tables required for each pair.
Calculate how many pair tables are required for each pair using the following formulas:
```
number-of-pair-tables-for-expansion = number-of-pair-tables-after-expansion - number-of-pair-tables-before-expansion
```
```
number-of-pair-tables-per-pair = ceiling ((number-of-pair-tables-per-pair / 36)
```
In the example, 'ceiling' refers to rounding up the value enclosed in parenthesis ( ) to the next integer.
Verify that the following numbers do not exceed the maximum number allowed on the storage system:
- The total numbers of current pair tables and pair tables required for expanding the capacity.
- The total numbers of current differential tables and differential tables required for expanding the capacity.
You can check the numbers of differential and pair tables in the Local Replication window.

Verify that all of the volumes used in SI meet the prerequisites.

Note: If only one volume capacity used in an SI pair can be expanded, while the other cannot be expanded, the resync operation of the SI pair cannot be performed after the expansion because the capacity of both the volumes is not the same. If the resync operation of the SI pair cannot be performed, perform the procedure in Troubleshooting the expansion of DP-VOL capacity.
Verify the pair statuses of the SI pairs.
The SI pair volume capacity can be expanded when the SI pairs are in the PSUS or PSUE status. Verify the current pair statuses of the SI pairs. If the pair statuses are not PSUS or PSUE, perform the pair operations, and then make sure that the pair statuses are migrated to PSUS or PSUE.
Expand the P-VOL capacity in the SI pair.
- When using CCI, add the -request_id auto option to the raidcom extend ldev command to specify the asynchronous command processing.
  Example:
```
raidcom extend ldev -ldev_id 0x4444 -capacity 10G –request_id auto -IH1
```
- When using HDvM - SN, expand the capacity in the Expand V-VOLs window.
Verify that expanding the P-VOL capacity in the SI pair is complete.
- When using CCI, use the raidcom get command_status command to verify that the raidcom extend ldev command processing is complete, and then verify that the LDEV capacity is correct using the raidcom get ldev command.
  Example:
```
raidcom get command_status -IH1
raidcom get ldev -ldev_id 0x4444 -fx -IH1
```
- When using HDvM - SN, select Logical devices from the Storage Systems tree, and then display the LDEV tab. Verify that the capacity with the target LDEV number is correct.
Expand the S-VOL capacity in the SI pair in the same way as the P-VOL capacity.

Note: If the S-VOL capacity in the SI pair cannot be expanded, perform the procedure in Troubleshooting the expansion of DP-VOL capacity.
Verify that expanding the S-VOL capacity in the SI pair is complete in the same way as the P-VOL capacity.
Verify that the volume capacity is not being expanded.
- When using CCI, check if the P column in the pairdisplay command displays N.
  Example:
```
# pairdisplay -g si -fxce -IM7
Group PairVol(L/R) (Port#,TID, LU-M) ,Seq#,LDEV#.P/S,Status, % ,P-LDEV# M CTG CM EM E-Seq# E-LDEV# DM P
si si00(L) (CL1-C-0,28, 0-0 )500000 30.P-VOL PSUS, 100 31 W - N - - - - N
si si00(R) (CL1-C-0,28, 1-0 )500000 31.S-VOL SSUS, 100 30 - - N - - - - N
```
  The P column displays the status that the volume capacity is being expanded:
  - N: The volume capacity is not being expanded.
  - E: The volume capacity is being expanded. This status displays for approximately 30 seconds after the expansion of the P-VOL or the S-VOL capacity is complete, and then this status is migrated to N.
- When using HDvM - SN in the Local Replication window, select the SI Pairs tab, then check if the Processing Status field is blank. (Expanding displays when the volume capacity is being expanded.) If the volume capacity is being expanded, wait for a while until the expansion is complete, and then verify the status.