You should not need to do anything. Proliants by default come with automatic RAID recovery option enabled. So, when you replace a faulty drive with a new one in a redundant array setup , raid rebuild starts automatically.
ACU or the management agensts will tell you the mirror rebuild progress. Once mirror rebuild is completed, the status should change to OK and you should also get a message in the "system" event log indicating the same.
if you have hardware problem than open a case with vendor (HP)
Regards,
Randhir
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