In general, people replace failed drives in production systems all day every day so any potential performance hit is generally not considered significant. However, the answer to your question unfortunately is "it depends." In general, the performance of that vdisk may suffer slightly while the array is rebuilt. However, if the controllers performance of the array are already maxed out then the rebuild may tax those controllers even move contributing to a potential system wide performance problem. You could explicitly set a 'utility-priority' if you want to lower the priority of the rebuild as to minimize contention. See page 81 of https://support.hpe.com/hpsc/doc/public/display?docId=emr_na-c01755995