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 certain combinations of
R5 instance types, such as r5.large,
r5.xlarge, r5.2xlarge, and r5.4xlarge, on
that host, within the host's physical core capacity.
The following instance families support Dedicated Hosts with multiple instance type support:
-
General purpose: A1 | M5 | M5n | M6i | M7i | T3
-
Compute optimized: C5 | C5n | C6i | C7i
-
Memory optimized: R5 | R5n | R6i | R7i
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 might be able to run certain combinations of R5 instances as
long as they are within 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 type. 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 types
can then be used to fill the host to core capacity. For the supported number of
instance types for each instance family, see the Dedicated Hosts Configuration
Table
The following table shows example instance type combinations:
| Instance family | Example instance type combinations |
|---|---|
R5 |
|
C5 |
|
M5 |
|
Considerations
Keep the following in mind when working with Dedicated Hosts that support multiple instance types:
-
Using multiple instance types on the same host is possible only within the same instance family.
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When mixing instance types, to maximize host utilization, we recommend launching larger instance types first followed by smaller instance types.
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Depending on the combination and launch order of the instance types on a Dedicated Host, it may not be physically possible to maximize the utilization of the host. When mixing instance types on a host, some capacity might be available on the host but not usable. For example, you might see 16 vCPUs available on an r5n host but may not be able to launch a 4xlarge instance on the host even though r5n.4xlarge runs on 16 vCPUs.
-
Note
If you enable an A1 Dedicated Host for multiple instance types, you can
launch only a mix of a1.xlarge and a1.2xlarge
instances on that host. If you launch an a1.medium or
a1.large instance on that host, you will be restricted to
launching only more of that same instance type on the host. A single
a1.4xlarge instance consumes all capacity on the host. If you
require a host for either a1.medium or a1.large
instances, we recommend that you allocate separate hosts for those instance
types.
