hi @poornakumar , is your server configured with any RAID levels? if so what is the RAID level?
if its using RAID, after you replace the disk, server will automatically start the rebuilding process and it will take some time depends on the RAID level and capacity. if its not started you can go to Disk utility and start the rebuild. but while its rebuilding performance will be bit lower. so plan at non-peak times.
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Good luck
KB