Generally, if you set auto-rebuild, yes. It's RAID5 though, so you're only protected from single drive failures. I use RAID6 on Areca cards (or better) for "critical" data, or remote servers -- single drive failures all too often become double drive failures before the RAID finishes rebuilding.

The other issue is that write (and sometimes read) performance is hurt during rebuild. For timing-sensitive systems, people often turn off auto-rebuild or scale back rebuild percentage of writes, so their application's performance isn't so affected. Of course, if the second failure happens during the rebuild...