ASM: moving disk between groups

SQL> select name||':'||path from v$asm_disk;

[..]
DATA_0008:/dev/oracleasm/disks/ASMDISK9

-- the operation
SQL> alter diskgroup DATA drop disk {chosen name from previous query} [rebalance power {speed between 0 and 11}];

-- the operation progress
SQL> select operation, state, est_minutes from v$asm_operation;

OPERA STAT EST_MINUTES
----- ---- -----------
REBAL RUN      7
REBAL WAIT      0

SQL> select GROUP_NUMBER,name,STATE from v$asm_disk where name='DATA_0008';

GROUP_NUMBER NAME       STATE
------------ ------------------------------ --------
    1 DATA_0008       DROPPING

-- ASM alert
Tue Sep 11 10:40:51 2018
NOTE: requesting all-instance membership refresh for group=1
Tue Sep 11 10:40:51 2018
GMON updating for reconfiguration, group 1 at 14 for pid 30, osid 19142
Tue Sep 11 10:40:51 2018
NOTE: group 1 PST updated.
SUCCESS: grp 1 disk DATA_0008 emptied
NOTE: erasing header (replicated) on grp 1 disk DATA_0008
NOTE: erasing header on grp 1 disk DATA_0008
NOTE: process _x000_+asm (19142) initiating offline of disk 8.3915952393 (DATA_0008) with mask 0x7e in group 1 (DATA) without client assisting
NOTE: initiating PST update: grp 1 (DATA), dsk = 8/0xe968b109, mask = 0x6a, op = clear
Tue Sep 11 10:40:51 2018
GMON updating disk modes for group 1 at 15 for pid 30, osid 19142
Tue Sep 11 10:40:51 2018
NOTE: PST update grp = 1 completed successfully 
NOTE: initiating PST update: grp 1 (DATA), dsk = 8/0xe968b109, mask = 0x7e, op = clear
Tue Sep 11 10:40:51 2018
GMON updating disk modes for group 1 at 16 for pid 30, osid 19142
Tue Sep 11 10:40:51 2018
NOTE: cache closing disk 8 of grp 1: DATA_0008
Tue Sep 11 10:40:51 2018
NOTE: cache closing disk 8 of grp 1: (not open) DATA_0008
Tue Sep 11 10:40:51 2018
NOTE: PST update grp = 1 completed successfully 
Tue Sep 11 10:40:51 2018
GMON updating for reconfiguration, group 1 at 17 for pid 30, osid 19142
Tue Sep 11 10:40:51 2018
NOTE: cache closing disk 8 of grp 1: (not open) DATA_0008
Tue Sep 11 10:40:51 2018
NOTE: group 1 PST updated.
Tue Sep 11 10:40:51 2018
NOTE: membership refresh pending for group 1/0xb68400e (DATA)
Tue Sep 11 10:40:51 2018
GMON querying group 1 at 18 for pid 16, osid 10242
GMON querying group 1 at 19 for pid 16, osid 10242
Tue Sep 11 10:40:51 2018
NOTE: Disk DATA_0008 in mode 0x0 marked for de-assignment
SUCCESS: refreshed membership for 1/0xb68400e (DATA)
NOTE: stopping process ARB0
NOTE: Attempting voting file refresh on diskgroup DATA
Tue Sep 11 10:40:54 2018
SUCCESS: rebalance completed for group 1/0xb68400e (DATA)

SQL> select operation, state, est_minutes from v$asm_operation;

no rows selected

SQL> select GROUP_NUMBER,name,STATE from v$asm_disk where name='DATA_0008';

no rows selected

SQL> alter diskgroup reco  add disk '/dev/oracleasm/disks/ASMDISK9';

Diskgroup altered

-- ASM alert entry
Tue Sep 11 10:45:43 2018
NOTE: Assigning number (2,1) to disk (/dev/oracleasm/disks/ASMDISK9)
NOTE: requesting all-instance membership refresh for group=2
NOTE: Disk 1 in group 2 is assigned fgnum=2
NOTE: discarding redo for group 2 disk 1
NOTE: initializing header (replicated) on grp 2 disk RECO_0001
NOTE: initializing header on grp 2 disk RECO_0001
NOTE: requesting all-instance disk validation for group=2
Tue Sep 11 10:45:44 2018
NOTE: skipping rediscovery for group 2/0xb78400f (RECO) on local instance.
Tue Sep 11 10:45:44 2018
NOTE: requesting all-instance disk validation for group=2
Tue Sep 11 10:45:44 2018
NOTE: skipping rediscovery for group 2/0xb78400f (RECO) on local instance.
Tue Sep 11 10:45:44 2018
GMON updating for reconfiguration, group 2 at 20 for pid 28, osid 20206
Tue Sep 11 10:45:44 2018
NOTE: group 2 PST updated.
Tue Sep 11 10:45:44 2018
NOTE: membership refresh pending for group 2/0xb78400f (RECO)
Tue Sep 11 10:45:44 2018
GMON querying group 2 at 21 for pid 16, osid 10242
NOTE: cache opening disk 1 of grp 2: RECO_0001 path:/dev/oracleasm/disks/ASMDISK9
GMON querying group 2 at 22 for pid 16, osid 10242
Tue Sep 11 10:45:44 2018
SUCCESS: refreshed membership for 2/0xb78400f (RECO)
Tue Sep 11 10:45:44 2018
SUCCESS: alter diskgroup reco  add disk '/dev/oracleasm/disks/ASMDISK9'
NOTE: Attempting voting file refresh on diskgroup RECO
Tue Sep 11 10:45:45 2018
NOTE: starting rebalance of group 2/0xb78400f (RECO) at power 1
Starting background process ARB0
Tue Sep 11 10:45:45 2018
ARB0 started with pid=31, OS id=20232 
NOTE: assigning ARB0 to group 2/0xb78400f (RECO) with 1 parallel I/O