This topic answers frequently asked questions (FAQs) about DDH.
What is a DDH?
An Alibaba Cloud Dedicated Host (DDH) is a cloud host that provides a single tenant with exclusive access to the resources of a physical server, which ensures isolation from other tenants at the physical server level. You can create ECS instances on a DDH. For more information, see What is a DDH?.
What are the benefits of DDH?
Subject to your license terms, you can bind your existing software licenses, such as those for Windows Server and Windows SQL Server, to ECS instances on a DDH. This reduces your cloud operational costs. DDH also provides the flexibility, visibility, and control to meet stringent compliance and regulatory requirements. For more information, see Benefits.
When should I purchase a DDH?
DDH can meet the requirements of specific use cases. For more information, see Use cases.
Is DDH a bare-metal product?
No. A DDH is a virtualized service that supports various host types. The host type that you select determines the instance type families and the number of ECS instances that you can create on the DDH. For more information about host types, see Dedicated host types.
What is the difference between a DDH and an EBM?
A DDH is a virtualized cloud server. An ECS Bare Metal Instance (EBM) is a compute product that combines the elasticity of virtual machines with the performance and features of physical servers. EBM is built on Alibaba Cloud's next-generation virtualization technology. For more information about EBM, see EBM instance types.
How do I create and release a DDH?
You can create a DDH in the ECS console. For more information, see Create a DDH.
If you do not renew a subscription DDH, it is automatically released upon expiration. For more information, see Dedicated host billing.
How do I view the available resources on a DDH?
You can view the total and available resources on a DDH in the following ways:
For information about the total resources of each host type, see Dedicated host types.
For a running DDH, you can view the available resources in the ECS console. For more information, see View and export information about a DDH.
Instance creation failure with sufficient resources
Typically, each dedicated host has two CPUs, labeled as Socket 0 and Socket 1. To maximize the performance of an ECS instance on a dedicated host, the ECS instance is created on a single socket.
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If one socket has available computing resources for creating the ECS instance, creation succeeds.
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If not, creation fails even if the combined available resources of both sockets are sufficient.
The following figure shows an example.
The following table lists the dedicated host types with socket information available and the number of sockets each type supports.
|
Dedicated host type |
Count of sockets |
|
Security-enhanced Memory-optimized r7t |
2 |
|
Security-enhanced General-purpose g7t |
2 |
|
Security-enhanced Compute-optimized c7t |
2 |
|
Security-enhanced Compute-optimized g6t |
2 |
|
Security-enhanced Compute-optimized c6t |
2 |
|
General-purpose Performance-enhanced g6e |
2 |
|
General-purpose g7 |
2 |
|
General-purpose g6 |
2 |
|
Memory-optimized Performance-enhanced r6e |
2 |
|
Memory-optimized r7 |
2 |
|
Memory-optimized r6 |
2 |
|
Compute-optimized Performance-enhanced c6e |
2 |
|
Compute-optimized c7 |
2 |
|
Compute-optimized c6 |
2 |
Migrating an ECS instance to a DDH
Yes. You can use the ECS console to migrate an ECS instance from a shared host to a DDH within the same account. After you restart the instance, it runs on the specified DDH. You cannot migrate subscription or preemptible instances. For more information, see Migrate an ECS instance from a shared host to a DDH.
Using BYOL on a DDH
To use your own licenses on a DDH, follow these steps:
Verify that your software license terms allow you to use your licenses on a dedicated host. You can consult a licensing advisor for assistance. After you confirm that your licenses are eligible, proceed to the next step.
Import a custom image by using the ECS console or by calling the ImportImage API operation. Alternatively, you can connect to an ECS instance and download the software directly. For more information, see Connect to an ECS instance.
Launch ECS instances that use these images on your DDH. You may need to use Key Management Service (KMS) to activate the instances or software. For more information about KMS, see What is Key Management Service?.
When you use a BYOL on a DDH, you may need to submit an audit form to your software provider. The form requires physical parameters of the DDH, such as the number of sockets, physical CPU cores, and vCPUs. You can find this information in the ECS console.
Does a DDH have a unique identifier?
Yes. Each DDH has a unique machine code, similar to a physical server's asset ID but different from the host ID. You can use this machine code to identify the DDH. When a DDH is allocated to your account, its machine code maps one-to-one with a specific physical server to help you track your assets.
Machine code reuse
No. A machine code is used for only one physical server. If your DDH is migrated to a new physical server, for example, due to a warranty expiration, Alibaba Cloud assigns a new machine code to your DDH that uniquely identifies the new physical server.
DDH automatic failover
Alibaba Cloud provides an auto failover service for DDHs. If you enable this service, your DDH is automatically migrated to a healthy host in case of a hardware failure. For more information, see Configure auto failover.
Selecting cloud disks and public bandwidth
You do not need to select cloud disks or public bandwidth when you create a DDH. You select these resources when you create an ECS instance on the DDH. For more information, see Create an ECS instance on a DDH.
Packet drops in UDP communication
When ECS instances on the same host communicate over UDP, the sending ECS instance may, in rare cases, calculate the checksum incorrectly. If the receiving ECS instance performs a strict checksum validation, it drops any packets with a mismatched checksum.
You can run the ethtool -K ethx tx off command on the sending ECS instance to disable checksum offload for the network interface.
Replace ethx with the network interface used for communication within the ECS instance, such as eth0.