Exadata : Shrink and Increase ASM Diskgroup

On our exadata half rack machine, two of our asm diskgroups were DATA2 with 3.5 TB and DATA1 with 11 TB.
We were planning to reduce DATA2 to 2 TB and DATA1 to 12.5 TB.

I followed below steps to accomplish the task:

[As we are using normal redundency about 50% of the size specified here will be usable]
step 1> resize from ASM. Resize DATA2 to 2 TB[4 TB raw] (form 88GB to 50 GB per GRIDDISK, in grididsk we should consider raw size)
SQL> ALTER DISKGROUP DATA2 RESIZE ALL SIZE 50 G REBALANCE POWER 11;

step 2> resize GRIDDISKs of DATA2_* on each cell for each griddisk run below command
CellCLI> ALTER GRIDDISK griddisk_name size=50G;
[
--create scripts using below query:
--as in exadata each cell is a failgroup use
--failgroup to generate script for a cell
select 'ALTER GRIDDISK ' || name || ' size=50G;'
from v$asm_disk
where name like 'DATA2_%' and failgroup='FAILGROUP';
]

step 3> check griddisk detail for DATA2 [size:]
$ cellcli -e "list griddisk where name like 'DATA2_.*' detail"|grep size:

step 4> check size of a DATA1 griddisk [size:]
$ cellcli -e "list griddisk where name like 'DATA1_.*' detail"|grep size:
-- let the size = CURR_GD [270G]

step 5> check free space on CELLDISKs [freeSpace:]
$ cellcli -e "list celldisk where name like 'CD_.*' detail"|grep freeSpace:
-- let free space = FREE_CD [38G]
-- we want to increase the size by FREE_CD
-- (here, FREE_CD has been freed by shirnking
-- each DATA2 gridisks to 25 GB)
-- so, new size of each griddisk of DATA1,
-- NEW_SIZE = CURR_GD+FREE_CD (in GB, raw size)
-- [308 G=270+38]

step 6> resize GRIDDISKs of DATA1_* on each cell for each griddisk run below command
CellCLI> ALTER GRIDDISK griddisk_name size=NEW_SIZE G;
[
--create scripts using below query:
--as in exadata each cell is a failgroup use
--failgroup to generate script for a cell
select 'ALTER GRIDDISK ' || name || ' size=NEW_SIZE G;'
from v$asm_disk
where name like 'DATA1_%' and failgroup='FAILGROUP';
]

step 7> resize from ASM
SQL> ALTER DISKGROUP DATA1 RESIZE ALL REBALANCE POWER 11; --no size specified to allocate maximum availabe space on related griddisks

step 8> check status of all asmdisks using "v$asm_disk"

step 9> check DB alert logs

step 10> check cell alert history on each cell
CellCLI>list ALERTHISTORY