Expanding the capacity of a DP-VOL used in a ShadowImage pair

You can expand the capacity of a DP-VOL that is used as a ShadowImage pair volume and is not shared with other replication software.

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 is performed after the expansion, or the first pair split operation is performed after a pair quick resync operation.

Therefore, the first pair resync operation after the expansion, or the first pair split operation after the pair quick resync operation 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 pool is not 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.

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:
The following command expands the capacity of LDEV#44:44 by 10 GB.
```
raidcom extend ldev -ldev_id 0x4444 -capacity 10G –request_id auto
```
Note: A maximum of 65,280 request IDs can be assigned to one storage system. If there is no available request ID, the command fails with EX_IDEXHA. If that occurs, see the description of the function of request IDs in the Command Control Interface Command Reference and release request IDs.
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 -request_id <request#>
raidcom get ldev -ldev_id 0x4444 -fx
```
Replace <request#> with the request ID that is displayed in step 3.
Confirm that asynchronous command processing has completed, and then release a request ID.
```
raidcom reset command_status -request_id <request#>
```
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.