Собсно вот
# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda2[1] sdb2[2]
970904192 blocks [2/1] [_U]
[=>...................] recovery = 5.2% (50561536/970904192) finish=15822.0min speed=969K/sec
А через несколько минут уже
# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda2[1] sdb2[2]
970904192 blocks [2/1] [_U]
[=>...................] recovery = 5.5% (53678080/970904192) finish=1996.8min speed=7653K/sec