Best Practices for Purchasing DeHs
Scenarios
Dedicated Host (DeH) provides dedicated physical hosts. You can create ECSs on a DeH to enhance isolation, security, and performance of your ECSs.
If you have specific requirements for the ECS resources, such as the number of ECSs, number of vCPUs, and memory size, you can calculate the number of DeHs required by referring to this document and determine the optimal order of provisioning ECSs.
This section describes how to purchase c6_pro DeHs and provision 20 c6.large.4 ECSs and 4 c6.12xlarge.4 ECSs.
Process
Step 1: Obtain the ECS List
List the ECSs to be provisioned. As shown in Table 1, 20 ECSs (each with 2 vCPUs and 8 GiB of memory) and 4 ECSs (each with 48 vCPUs and 192 GiB of memory) need to be provisioned.
Step 2: Adjust the ECS Flavors
Adjust the ECS flavors in the ECS list to those supported by the DeH flavor family.
For details, see ECSs Allowed on DeHs.
Step 3: Calculate the Number of DeHs to Be Purchased
Solution 1: Accurate calculation
Calculate the number of DeHs to be purchased based on the information about all ECSs to be purchased. This solution is suitable for provisioning a few ECSs with a few types of flavors.
Before the calculation, view the DeH flavor information and the NUMA topology information about the supported ECS flavors. For details, see Categories and Types.
- Sort the ECSs to be provisioned in descending order of flavors.
For example, 20 ECSs of the c6.large.4 flavor and 4 ECSs of the c6.12xlarge.4 flavor need to be provisioned, as shown in Table 2.
- Prepare an editable table and add one DeH to the initial resource pool.
For example, if the selected DeH flavor is c6_pro, the initial resource pool information is shown in Table 3.
- Obtain the first resource in the first row from the ECSs to be purchased in Table 2.
Based on Table 2, calculate the resources as follows:
- Required ECSs: Decrease by 1.
- ECSs already provisioned: Increase by 1.
Based on Table 3, calculate the resources as follows:
- Used resources: Enter the vCPUs and memory of the resources by NUMA based on Table 2.
- Available resources: Total resources – Used resources
For example, after calculation, one ECS can be provisioned and is deducted from the required resources in the table. Table 4 shows the ECS list after resource deduction, and Table 5 shows the resource pool after calculation.
- Based on the DeH resource pool information, calculate the resources in Table 2 in sequence and check whether the DeH can provision an ECS.
Check the topology information of the ECSs and DeH. If the vCPUs and memory in the DeH resource pool are greater than those of the ECS, the ECS can be provisioned.
- Add one DeH to the resource pool and repeat the operation in step 3.
Table 6 Resource pool (one DeH added) DeH Name
NUMA Information
Resource Type
Total Resources
Used Resources
Available Resources
DeH1
NUMA 0
vCPUs
36
24
12
Memory (GiB)
144
96
48
NUMA 1
vCPUs
38
24
14
Memory (GiB)
152
96
56
DeH2
NUMA 0
vCPUs
36
0
36
Memory (GiB)
144
0
144
NUMA 1
vCPUs
38
0
38
Memory (GiB)
152
0
152
- Repeat steps 3 to 5 until all resources in Table 2 are provisioned, that is, no required resources are available in all rows.
According to the calculation, you need to purchase four DeHs of the c6_pro flavor to provision 20 ECSs of the c6.large.4 flavor and four ECSs of the c6.12xlarge.4 flavor.
Table 7 ECS list (after purchase) vCPUs
Memory (GiB)
NUMA Nodes
Required ECSs
ECSs Already Provisioned
48
192
2
0
4
2
8
1
0
20
Table 8 Resource pool (after purchase) DeH Name
NUMA Information
Resource Type
Total Resources
Used Resources
Available Resources
DeH1
NUMA 0
vCPUs
36
36
0
Memory (GiB)
144
144
20
NUMA 1
vCPUs
38
38
0
Memory (GiB)
152
152
12
DeH2
NUMA 0
vCPUs
36
36
0
Memory (GiB)
144
144
20
NUMA 1
vCPUs
38
26
12
Memory (GiB)
152
104
48
DeH3
NUMA 0
vCPUs
36
24
12
Memory (GiB)
144
96
48
NUMA 1
vCPUs
38
24
14
Memory (GiB)
152
96
56
DeH4
NUMA 0
vCPUs
36
24
12
Memory (GiB)
144
96
48
NUMA 1
vCPUs
38
24
14
Memory (GiB)
152
96
56
Solution 2: Fuzzy calculation
Calculate the required resources using information about all ECSs to be purchased. Then, calculate the number of DeHs to purchase based on the average allocation rate. This solution is suitable for buying a large number of ECSs with various flavors. This solution may be inaccurate because it uses the average allocation rate as a reference.
- Collect resource information of all ECSs to be purchased and calculate the total number of vCPUs and memory capacity.
- Divide the total memory capacity by the total number of vCPUs to obtain the memory-to-vCPU ratio. Compare the ratio with that of DeHs. If the ratio is higher than that of DeHs, the memory is used for calculation. Otherwise, the vCPUs are used for calculation.
- Use the experience-based allocation rate as the standard rate to purchase DeHs.
Table 9 Allocation rate (experience-based) Average vCPUs of Resources to Be Provisioned
Average Allocation Rate
< 32 vCPUs
85%
≥ 32 vCPUs
70%
- Calculate the number of DeHs to be purchased based on the following formula:
Number of DeHs to be purchased = Ceiling (Total resources/Number of resources per DeH/Average allocation rate)
Step 4: Provision ECSs
Recommended provisioning sequence:
To provision as many ECSs as possible, you are advised to provision ECSs in descending order of flavors, which means provisioning large-specification ECSs first and then small-specification ECSs.
For details about how to provision ECSs on a DeH, see Deploying ECSs on DeHs.
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