Amazon EC2 Dedicated Host instance capacity configurations
Dedicated Hosts support different configurations (physical cores, sockets, and VCPUs) that allow you to run instances of different families and sizes.
When you allocate a Dedicated Host in your account, you can choose a configuration that supports either a single instance type, or multiple instance types within the same instance family. The number of instances that you can run on a host depends on the configuration you choose.
Single instance type support
You can allocate a Dedicated Host that supports only one instance type. With this configuration, every instance that you launch on the Dedicated Host must be of the same instance type, which you specify when you allocate the host.
For example, you can allocate a host that supports only the
m5.4xlarge instance type. In this case, you can run only
m5.4xlarge instances on that host.
The number of instances that you can launch onto the host depends on the number of
physical cores provided by the host, and the number of cores consumed by the
specified instance type. For example, if you allocate a host for
m5.4xlarge instances, the host provides 48 physical cores, and each
m5.4xlarge instance consumes 8 physical cores. This means that you
can launch up to 6 instances on that host (48 physical cores / 8 cores per
instance = 6 instances).
Multiple instance type support
You can allocate a Dedicated Host that supports multiple instance types within the same instance family. This allows you to run different instance types on the same host, as long as they're in the same instance family and the host has sufficient instance capacity.
For example, you can allocate a host that supports different instance types within
the R5 instance family. In this case, you can launch any combination of
R5 instance types, such as r5.large,
r5.xlarge, r5.2xlarge, and r5.4xlarge, on
that host, up to the host's physical core capacity.
The following instance families support Dedicated Hosts with multiple instance type support:
-
General purpose: A1, M5, M5n, M6i, and T3
-
Compute optimized: C5, C5n, and C6i
-
Memory optimized: R5, R5n, and R6i
The number of instances you can run on the host depends on the number of physical
cores provided by the host, and the number of cores consumed by each instance type
that you run on the host. For example, if you allocate an R5 host,
which provides 48 physical cores, and you run two r5.2xlarge instances
(4 cores x 2 instances) and three r5.4xlarge
instances (8 cores x 3 instances), those instances consume a
total of 32 cores, and you can run any combination of R5 instances as
long as they do not exceed the remaining 16 cores.
However, for each instance family, there is a limit on the number of instances
that can be run for each instance size. For example, an R5 Dedicated Host
supports a maximum of 2 r5.8xlarge instances, which uses 32 of the
physical cores. In this case, additional R5 instances of smaller sizes
can then be used to fill the host to core capacity. For the supported number of
instance sizes for each instance family, see the Dedicated Hosts Configuration
Table
The following table shows example instance type combinations:
| Instance family | Example instance size combinations |
|---|---|
R5 |
|
C5 |
|
M5 |
|
Considerations
Keep the following in mind when working with Dedicated Hosts that support multiple instance types:
-
With N-type Dedicated Hosts, such as C5n, M5n, and R5n, you can't mix smaller instance sizes (
2xlargeand smaller) with larger instance sizes (4xlargeand larger, includingmetal). If you require smaller and larger instance sizes on N-type Dedicated Hosts at the same time, you must allocate separate hosts for the smaller and larger instance sizes. -
We recommend that you launch larger instance types first, and then fill the remaining instance capacity with smaller instance types as needed.
