This topic provides answers to some frequently asked questions about Classic Load Balancer (CLB).
How do I choose among the specifications for high-performance CLB instances?
Can I change the specification of a high-performance CLB instance?
Can I associate an EIP with an Internet-facing CLB instance?
Can I change the primary and secondary zones of a CLB instance?
How do I choose among the specifications for high-performance CLB instances?
Pay-as-you-go instances
If your workloads expect only minor fluctuations, we recommend that you select pay-by-specification. You are charged a specification fee on an hourly basis based on the specification that you select.
If your workloads expect periodic or large fluctuations, we recommend that you select pay-by-LCU. Pay-by-LCU CLB instances can automatically scale resources on demand. In addition, you do not need to specify a specification. You are charged for consumed LCUs on an hourly basis.
Why is a high-performance CLB instance unable to reach the performance limit defined in the specification?
This issue can be explained by the cask theory.
High-performance CLB instances do not guarantee that the three metrics can reach the upper limits of a specification at the same time. If one of the metrics reaches the upper limit, the instance performance is limited.
For example, you purchase a high-performance CLB instance of the slb.s3.small specification. When QPS reaches 20,000, new connection requests are dropped by the CLB instance even if the number of concurrent connections has not reached 200,000.
Can I change the specification of a high-performance CLB instance?
Yes, you can upgrade a shared-resource CLB instance to a high-performance CLB instance.
you can change the specification of a high-performance CLB instance in the CLB console. For more information, see Modify the configurations of pay-as-you-go CLB instances.
You can change only shared-resource CLB instances to high-performance ones. You cannot change high-performance CLB instances to shared-resource ones.
When you upgrade a shared-resource CLB instance to a high-performance CLB instance, your services are not affected and the IP address of the CLB instance remains unchanged.
We recommend that you upgrade a shared-resource CLB instance to a high-performance CLB instance during off-peak hours. You can also configure DNS resolution to replace your current load balancing service before you upgrade the CLB instance.
The IP addresses of CLB instances remain unchanged when you change instance specifications.
Why does the instance specification remain unchanged after I change the specification of a high-performance CLB instance?
If you change the metering method (pay-by-bandwidth or pay-by-data-transfer) when you change the specification of a high-performance CLB instance, the new instance specification and the new metering method take effect at 00:00:00 the next day.
Can I associate an EIP with an Internet-facing CLB instance?
No, this is not supported.
Instead, you can use the following methods to enable SLB instances to use EIPs for Internet communication:
Purchase an internal-facing CLB instance and associate an EIP with the CLB instance. For more information, see Create and manage a CLB instance and Associate and manage an EIP.
Purchase an Internet-facing ALB instance. By default, an EIP is associated with the Internet-facing ALB instance to enable Internet access. For more information, see Create an ALB instance.
Purchase an Internet-facing NLB instance. By default, an EIP is associated with the Internet-facing NLB instance to enable Internet access. For more information, see Create and manage an NLB instance.
Can I change the primary and secondary zones of a CLB instance?
No, you cannot change the primary and secondary zones of a CLB instance.
You can purchase a CLB instance and specify a different primary or secondary zone for the CLB instance.
ALB and NLB support more flexible zone policies. We recommend that you use ALB and NLB. For more information, see What is SLB?, What is ALB?, and What is NLB?