(Old question with an answer still valuable) In a SHC the SH resources are not shared among searches, but for scheduled searches. Ad-hoc searches running on a SHC member will consider the cpu cores and memory resources as if it was unique. For the scheduler, the captain will mitigate starvation by distributing scheduled jobs to available members. Each member not being supposed to consume more than its capacity. So you give more resources to scheduled jobs automatically in a SHC, while for adhoc searches it depends on where the users are logged in. A load balancer for users connections can help, for high availability: users don't need to know each member fqdn nor ipod address to get in.
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