ASM Recovery on RAC

I have 2 instances of Oracle RAC.
All disk resources on which problem occured are exported via iSCSI and managed by ASM.
One of the iSCSI server had a power faiure, which last longer than 6h

DISKGROUP DATA is mirrored via ASM between /dev/raw/11 and /dev/raw/raw21

in v$asm_disk i have

DATA_0000	MEMBER	/dev/raw/raw11
_DROPPED_0001_DATA	UNKNOWN ''
''	MEMBER	/dev/raw/raw21

DATA_0001 should have path /dev/raw/raw21

To recover database, should i do :
alter diskgroup DATA DROP DISK _DROPPED_0001_DATA FORCE; and then
ALTER DISKGROUP DATA ADD DISK '/dev/raw/raw21' FORCE;

or just
ALTER DISKGROUP DATA ADD DISK '/dev/raw/raw21' FORCE;

or there is some other scenario for rocovery

-- 
Regards
Ygnacy