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Dedicated instances limit a server to a single user, who traditionally had little control or visibility over where dedicated and nondedicated instances resided. Amazon EC2 Dedicated Hosts give IT teams more control over workload placement -- ensuring that workloads reside on the right servers without having to move between physical servers.
Both Dedicated Instances and Hosts support dedicated physical servers, but EC2 Dedicated Hosts provide visibility of the server's sockets, cores and host ID. This allows affinity between a host and an instance, enabling the instances to restart on the same server after it has stopped. EC2 Dedicated Hosts also enable developers to place instances and add capacity through allocation requests.
An Amazon EC2 Dedicated Host represents the server, and that server can support multiple instances of the same type. For example, a c3.xlarge Dedicated Host provides two sockets and 20 cores to support up to eight c3.xlarge EC2 instances.
IT teams can gain visibility and control over EC2 instances in a Virtual Private Cloud by placing them on specific servers, enabling complementary workloads to communicate more efficiently. IT also can control the amount of load on a particular server to improve performance and limit instances to specific servers to improve security and meet governance and regulatory requirements.
But EC2 Dedicated Hosts also pose several limitations. For example, developers can't use Amazon Machine Images for Windows, RHEL or SUSE. In addition, EC2 Auto Recovery, Auto Scaling, placement groups and Amazon Relational Database Service instances won't work with Dedicated Hosts.
EC2 Dedicated Hosts are available on-demand and priced according to the instance type you select. You can also purchase EC2 Dedicated Hosts at reserved prices, which can save money because they're long-term commitments. Compute-, memory- and storage-optimized hosts are also available.
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