Hi Sun Ww,
Are you using an HDP release? My guess is not. This forum is best served when you’re running HDP. If not, you’re better off contacting the hbase user mailing list.
That said, you’ll need to provide more information about your configuration and what the RS was doing at the time. Do you have RS logs from that time window? Are you using the default memstore and blockcache size? How many regions are being served? How large are they? What’s the workload (is it particularly read or write heavy)?