Hi garimayadav -
Questions asked by you purely depends upon data volume/day, underlying hardware, deployment architecture, network latency. Following links will address your queries. Please have a look.
http://docs.splunk.com/Documentation/Splunk/6.2.2/Capacity/Forwarder-to-indexerratios
http://docs.splunk.com/Documentation/Splunk/6.2.2/Capacity/Referencehardware
http://docs.splunk.com/Documentation/Splunk/6.2.2/Capacity/Performancechecklist
http://docs.splunk.com/Documentation/Splunk/6.2.2/Capacity/Summaryofperformancerecommendations
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