A dedicated host is a physical server that is intended solely for hosting your VMs in Yandex.Cloud. VMs on dedicated hosts have all the features of regular VMs plus they're physically isolated from other users' VMs. You can also distinguish your VMs used for different projects:
You can create a group of one or more dedicated hosts of the same type. To optimize the use of resources, you can host multiple VMs with different configurations on each dedicated host.
Advantages of using dedicated hosts:
- Security and compliance.
You can use a dedicated host to physically isolate your VM in the public cloud if this is required by your company's information security service or industry standards (such as medical or finance).
- Using your own licenses.
If your company has licenses from Microsoft or other vendors that require linking to physical resources, you can use them in Yandex.Cloud following the
Bring your own license(BYOL) model.
- Managing your VM placement.
You can choose which dedicated host to run your VM on or allow Compute Cloud to do it automatically.
Types of dedicated hosts
Characteristics of dedicated hosts:
||Intel® Xeon® Gold 6230||2||40||66*||454|
* Intel Xeon Gold 6230 has 80 vCPUs available, but 14 of them are used by the system.
Fragmentation of host's physical resources
Two processors are installed on a physical server. However, not all of their cores are available for running VMs. Some cores are allocated for system usage.
For example, a dedicated host with two Intel® Xeon® Gold 6230 processors can use 66 vCPUs to run VMs (34 on the first processor and 32 on the second). The remaining 14 vCPUs (6 + 8) are used by the system.
When creating a VM on a dedicated host, you may encounter resource fragmentation: the number of free vCPUs is sufficient, but you can't run your VM. For example, you can only run 10 VMs with 6 vCPUs each on a dedicated host with 66 vCPUs.
In this case, you can run 2 VMs with 2 and 4 vCPUs to use the dedicated host's vCPUs at full capacity.
When creating a host group, specify the number of dedicated hosts. When updating the group, you can reduce or increase the number of hosts in it. The scaling policy is defined by the
yc compute host-group create \ --fixed-size <number of hosts> \ ...
||The number of dedicated hosts in the group.|
Compute Cloud stops VMs during maintenance without moving them to other hosts. Subsequent VM behavior depends on the physical server status.
If the physical server is restarted, the VMs running on it are automatically restarted, too, and linked:
- To the same host group if the VM was linked to any group. Linking to a different host in the group is possible.
- To a dedicated host if the VM was linked to a specific host.
The maintenance policy is set when creating a group of dedicated hosts and defined by the
yc compute host-group create \ --maintenance-policy restart \ ...
If the physical server is completely stopped, Compute Cloud:
- Disables access to your dedicated host.
- Deletes the physical server and its unique ID (
server-id). In this case, the IDs of the host group (
host-group-id) and each dedicated host (
host-id) are preserved.
- Replaces failed hardware and assigns a new ID.
- Moves VMs from faulty to new hardware according to the VM linking rules.
Linking a VM to a group or host
To uniquely map a VM and a physical server, you can create a VM that is linked:
- To a group of dedicated hosts.
When the VM is stopped, it won't be available on the group hosts, and when it's restarted, it may be linked to a different host from the group.
- To the selected host from a group of hosts.
When the VM is stopped, it won't be available on the host, and when it's restarted, it will be linked to the same host from the group.
Linking a VM ensures that it will run on the same physical server or group of servers even after a scheduled outage.
To move a VM from one dedicated host to another:
- Stop the VM.
- Link the VM to a different host in the group.
- Restart the VM.
When creating a VM, you can specify multiple host groups or specific hosts that it can be linked to. Example of linking a VM to a host group:
yc compute instance create \ --host-group-id 1 \ --network-interface subnet-name=default-ru-central1-a \ --zone ru-central1-a
In this case, the VM will be linked to one of the specified host groups:
done (33s) id: abcdefghigklm12no3pq folder_id: a1b23cd45efg6higklmn created_at: "2020-09-08T20:19:41Z" zone_id: ru-central1-a platform_id: standard-v2 resources: memory: "2147483648" cores: "2" core_fraction: "100" host-group-id: 2 ...
For information about pricing for dedicated hosts, see Dedicated host usage.